Archive of Our Own

Chapter Text

Katsuki has been sick for a month. At first, he just thought he was tired from the jet lag and time zone change to America. Then, he thought it was a stubborn cold. After two weeks of feeling like shit, he started to think that he must be allergic to the country itself because something was not right.

He’s been having constant headaches and fevers. He can’t get comfortable when he sleeps, or really ever. He gets random shooting pains in his abdomen, but he hasn’t had a heat in years; his suppressants make sure of that.

Katsuki pushes through the discomfort during his patrols and meetings. He’s tried painkillers, allergy medication, teas, everything. He went to the doctor, but all they did was prescribe a migraine medication that said on the bottle it shouldn’t be taken with suppressants. Which he will not be going off of. Great. The doctor ordered him an ultrasound, but he would have to pay out of pocket since his travel insurance doesn’t cover “reproductive care”. Even better. 

Katsuki didn’t bother with the ultrasound. He doesn’t have a spare five hundred dollars laying around. Besides, he’s sure he’s just tired from the move and the emotional stress of hauling ass across the world after getting his heart broken. 

Things take a turn for the worse when he wakes up late one morning for his 6am patrol. Shit. He never wakes up late. He throws himself out of bed, only for his legs to not catch him. He crumples to the floor and then summons what little dignity he has left to gingerly pull himself back up against the bed. His vision swims. He knows he’s going to vomit. It’s only a matter of time. He grabs his phone and slowly makes his way over to the bathroom, propping himself up next to the open toilet. Even that movement has him winded and sweating. There’s a pit in his stomach, like someone’s hand has clenched around his organs. 

He calls his manager to let him know he’s sick and won’t be able to do his patrol. Katsuki hates taking unexpected days off. He’s not a slacker, and he’s certainly not weak, but as soon as he hangs up, he’s throwing up into the toilet. Better to do that here than on the street in the middle of a patrol anyway.

In a way, Katsuki is relieved. This must be the illness his body has been working up to, and maybe if he takes a day off he’ll get it out of his system. He spends the day in bed, chugging water with electrolytes. He orders miso soup from the closest japanese place he can find and it’s not half bad, but he would do anything for a taste of his mother’s. Alone in this empty, sterile apartment, the sharp pang of loneliness that’s been chasing him since leaving Japan a month ago finally catches up to him.

It’s only made worse by the fact that it’s been over a month since he’s spoken to Izuku. Katsuki feels Izuku’s absence just as acutely as his illness. No calls, no texts. No random check ins, no sending links at all hours of the night to whatever pointless online hero discourse extras are talking about. Izuku always keeps Katsuki updated with that nonsense, and he doesn’t care, not really, but he likes to hear Izuku’s opinions. He likes to hear Izuku rant about something they both know is largely pointless.

But it’s been silence. Nothing. The routine of their friendship has been ingrained into Katsuki’s life for the past eight years. They see each other at least once a week, sometimes to get takeout and watch a movie at one of their apartments, or to go grocery shopping together, or to go to a concert, or have a joint patrol. If for whatever reason they don’t see each other, they talk on the phone. Izuku loves texting - he’ll send paragraph after paragraph in seconds. He never runs out of topics to bring up. 

Katsuki has about five words of text in him on a daily basis. Sending a message feels akin to literally ripping his own teeth out, so he calls people instead. He’ll call his mother so she can tell him about whatever her latest project is, or he’ll call Kirishima to hear what his gym and meal prepping routine is this week, or he’ll call Mina for advice on an outfit, or Jirou will call with a link to her playlist of the week. Katsuki will pick his favorites and then the next time they call, he’ll tell her his favorites.

Squeezed in so many other moments is Izuku’s voice. He’s the only person Katsuki lets be a part of his daily, intimate life. Izuku isn’t the type of friend he’ll reserve for certain interests - no, they tell each other everything about every aspect of their lives. Or at least they did, before Izuku decided Katsuki didn’t need to know about all the omegas he’d been fucking. And if Izuku could keep such a big secret, how many other secrets could he be keeping? Did Katsuki truly know him at all?

Since the last text message that Katsuki sent Izuku, mere hours before leaving the country, it’s been radio silence. I need some distance, Katsuki had said. I’m leaving tomorrow for an overseas mission and I need to be focused.

Izuku’s reply had been surprisingly supportive. I’ll always be here for you, Kacchan. If you need me, I’m only a phone call away.

And then, nothing. For over a month. In hindsight, Katsuki doesn’t know what he was expecting. He kept it pretty vague in his message. He thought Izuku would at least have some questions, or at most call him demanding why the fuck he’d signed up for an overseas mission and then failed to mention it until the day he was leaving. But Izuku didn’t seem to mind. So Katsuki let it stay that way. If Izuku didn’t care, then Katsuki wouldn’t either. If Izuku didn’t want any additional explanation, Katsuki wouldn’t provide it.

Katsuki knew this mission would be lonely - that was the point. Completely isolate yourself from your typical daily life, remove everyone including the person you want to avoid most, kick some ass abroad, then return with a clear head. It sucked for the first few weeks, like he expected, but then it just kept sucking, and now he’s sicker than he’s ever been in his adult life.

The day after calling out, Katsuki wakes up feeling even worse. He calls out from work again. His mind is full of fog and his limbs full of lead. He sleeps and eats and tries not to check his phone every ten minutes for a name he knows won’t be there.

The next morning, he wakes up to his alarm. His head still feels like it’s filled with cotton, but he can’t call out again. He doesn’t want to lose multiple days of this mission abroad. It’s a short program, only three months long, and he doesn’t want to sacrifice international connections. Regardless, Katsuki has never called out more than two days in a row. He’s not going to start now. So he drags his sorry ass out of bed, dons his hero gear, and makes his way to the agency. He survives most of the morning with little issue. The other employees already know he isn’t one for small talk, and he gets through his morning meetings with minimal contribution. His mind fades in and out of the conversation, unable to focus for more than a few minutes at a time due to the pounding headache behind his eyes.

It’s a relief when he’s finally freed to go on his routine patrol. Most days are quiet, since the majority of the action of this mission is meant for the few underground villains they’re trying to track down. He’s only run into two villains on his daily patrols here so far and was able to take them down in a matter of minutes.

Katsuki starts on his usual route, but within ten minutes, he knows something isn’t right. The headache hasn’t gone away despite taking painkillers, and now nausea rolls through his body in waves. Even in the tail end of spring, the heat coming up from the city pavement is stifling. The air is thick with humidity, pasting Katsuki’s hair to his forehead. Usually the heat doesn’t bother him - this weather is a dream for his quirk. He could probably blow up a whole city block with the amount of sweat he’s got if he didn’t feel so damn weak. Every step feels weighted, and soon, Katsuki doesn’t know how he’s going to make it back to the agency, much less make it through the remaining six hours of his patrol. 

He stops by a convenience store, soaking in the air conditioning as much as he can. He buys a bottle of water just so he can feel the cold condensation against his face. As he chugs it, he hopes it’ll actually do something to lower his body temperature. When he steps back out, the heat feels even worse than it did before. He looks to other pedestrians, but they all seem normal and not like the sun is somehow a couple thousand miles closer today.

Just make it back to the agency, Katsuki tells himself, shame churning in his gut. He should have taken another day off. He makes his way back through his patrol route, slow and steady. 

His eyelids are so heavy, and each step he takes is basically a shuffle. He blinks and reopens his eyes to find himself halfway down a block. Did I space out? Did I just keep walking with my eyes closed?

A shining beacon of hope sits at the end of the block. A bench. Fuck returning to the agency. Katsuki’s going to sit and he’s going to figure out what the fuck is going on. And maybe order a cab back home. This just keeps getting more embarrassing.

Katsuki shuffles towards the bench, but his foot catches on a crack in the sidewalk. He tries to catch himself and fails, slamming into the concrete face first. He doesn’t get up.

~~~

The next three days are a blur. He remembers paramedics around him on the sidewalk and being carted into the back of an ambulance. He remembers being somewhat lucid in an American hospital, a doctor telling him that they don’t know exactly what’s wrong, even after running multiple scans. She’s trying to ask him questions about his symptoms, but her words float around his brain, refusing to connect in a way that makes sense. He is sure of one thing, however. This isn’t any regular sickness. He gets the occasional flu or cold, but the overwhelming fatigue, heat, and abdominal cramping only point to one thing.

He manages to choke out one word to the doctor. “Heat.”

It shouldn’t be possible. Katsuki hasn’t had a heat since he was fifteen years old. His heats were always horrific, debilitating his whole body for at least a week. When he started at UA, he was determined to leave all that shit behind. He was training to be a hero, and he would be number one, hormones be damned. He didn’t have time for that shit, so he insisted on being put on the strongest suppressants his doctor could approve. His symptoms had almost entirely disappeared, along with his heats. But now, the insatiable itch crawling under his skin can only point to one thing.

With the newfound lead, the doctors take Katsuki through another round of scans and examinations. He does get that ultrasound, and he’s just present enough to hope that whatever clown files his paper work deems this as emergency care instead of reproductive care.

The words imprinted and mate and the best care for you will be back in Japan are what he’s able to piece together from the debrief with his doctor. He’s given pain meds that knock him out and a personal guide to accompany him on a flight back to Japan. If Katsuki could form a coherent thought, he’d be screaming at these people that they’re ruining his mission, to get their nitrile gloved fingers out of his career. But he doesn’t have the mental or physical capacity to fight them, so he watches from a plane window as America fades beneath him. He gets another round of meds, and sleeps the whole flight home.

When Katsuki wakes up, he’s back in the hospital. His mind lurches for a moment, wondering if his tentative diagnosis and flight back to Japan was all just fever induced hallucinations. Maybe his body temperature got so high it cooked his brain and he really is losing it this time. Except when the nurse walks in, she gives him a smile and greets him in Japanese. Katsuki lets out a sigh of relief. 

She takes his vitals and makes small conversation. She tells him that he’s doing much better, that he’s in the Musutafu hospital after being flown back to Japan. Katsuki didn’t ever think he’d be happy to be in a hospital, but seeing the familiar pattern of the curtains of his home hospital fills him with comfort and familiarity. He has been here more times than he can count. After a month of living in a foreign country, even the smallest part of home is a relief.

She tells him his vitals all look fine and much better than when he arrived. She leaves with a smile and a promise that the doctor will be in shortly. After twenty minutes of attempting to sort through his jumbled, heat ridden memories of the past few days, Katsuki hears a knock at the door.

A shorter woman with pin straight, shoulder length hair steps in. She greets Katsuki with a firm handshake that he struggles to return. “Hello, Bakugou-san. I’m Doctor Hirata, the head gynecologist here. It’s nice to meet you.” She pulls up a chair to Katsuki’s bedside and steeples her fingers. “How are you feeling?”

He stares for a moment, not sure what the proper response is after being incoherent for three days. “Like shit.”

“I would imagine so,” she says with a small smile. “You’ve been through quite the ordeal these past few days. Why don’t you walk me through your symptoms?”

Katsuki takes her through the past month, explaining the continual illness since stepping foot in the US and its gradual yet debilitating progression. She listens without taking her eyes from Katsuki. 

“When was your last heat?”

“When I was fifteen.”

“So you’ve been taking suppressants since then?”

Katsuki nods. She pauses for a moment.

“Are you in a relationship with anyone?”

Irritation prickles at Katsuki’s skin. “No.” His face gets hot. “And I’m not, like, active either.”

“So no chance of pregnancy?”

Katsuki has to keep his eyes from bugging out of his head. “Definitely not.” 

Not that he doesn’t maybe want to have kids, but over the past few years, he’s accepted some truths about what the rest of his life is probably going to look like. Katsuki knows, deep down where his omega instincts reign, he doesn’t want anyone but Izuku. He doesn’t want mating, or kids, or any of it with anyone else. 

Even as a belligerent and mean child, he was fixated on Izuku. It was easier for Katsuki to put Izuku down, to make fun of the very things that made his heart hammer in his chest.

But then Izuku got into UA. And then he got a quirk. And then, as if all that wasn’t enough, he presented as an alpha and Katsuki presented as an omega. Izuku presented first, some time between the entrance exam and the first day of school. He came to UA with a strong ass quirk, All Might as a mentor, and new alpha pheromones. He was a natural leader, a magnet that drew together the strength of the class. It made Katsuki sick.

It only got worse when Katsuki presented. Izuku was a dweeb who was getting stronger by the day. Katsuki couldn’t stand him but couldn’t get him out of his head. And then one day, when he walked into class, he was hit by a wall of scent - the deep rich scent of pine, like an old forest in the coldest part of winter. It burned through his lungs, clearing his head of anything but Izuku, Izuku, Izuku. An entire additional sense had been opened to him, and all his body cared about was getting enough of Izuku’s scent.

It got worse before it got better. But ultimately, when Izuku left UA to be a vigilante, he was gutted. Because Izuku was a self sacrificing asshole. Because Izuku thought he could do it all on his own. Because they were still fucking sixteen years old and Izuku didn’t deserve this. But almost more pressing than each of those reasons, his scent was gone from Katsuki’s life. And very quickly Katsuki realized how much he’d come to expect it - in the showers after a hard sparring session, or from behind him during class, or in the kitchen late at night. The absence of it left Katsuki raw and aching. On one occasion (that he was not particularly proud of) he went into Izuku’s room just to calm himself down. Just to be reminded that Izuku was still alive even if he wasn’t there, with Katsuki, as he was always meant to be. In that dark empty room, Katsuki let himself breathe Izuku in and admit that he needed the other boy. 

Because that was the problem, wasn’t it? Katsuki and Izuku had never really been apart for any significant amount of time. Even when they weren’t friends they were still in the same classes or walking home on the same street. No time in Katsuki’s life has been devoid of Izuku. The longest they’d been apart was those weeks during the war, and this past month of Katsuki being in the US.

“Always best to explore every option,” Dr. Hirata says. “So no relationship, but is there someone you’re particularly close to? Someone you would have been separated from while abroad?”

Katsuki stares in shocked silence. How would she know…“Yes. A long time friend.”

She nods. “What’s the longest you two have been apart from each other? Not just a few days or a few miles, but significantly separated for a long stretch of time?”

Katsuki doesn’t like where this is going. “A month. The month that I was abroad, just now. Before that, only a few weeks, and that was years ago.”

Dr. Hirata pauses to move towards her computer and type for several minutes. Katsuki sits in progressively itchier silence, waiting for the inevitable ball to drop. He doesn’t know what this could possibly have to do with Izuku, but based on the pensive look on the doctor's face and her delayed response, it can’t be good.

“We’ll have to run a few more tests and some bloodwork now that we know what we’re looking at. It took way too long for you to be paired with a gynecologist, and that’s the care you’ve been needing this whole time it seems. We’ll run an analysis on your hormone levels and several other omegan characteristics, okay?”

Katsuki tries to rein in the frustration bubbling just beneath the surface. “Cut the bullshit. What does Izuku have to do with my hormone levels? How did you know to ask those questions?”

“I don’t want to give you a definitive answer before we’ve run these tests, but what I’m currently suspecting is that you’ve imprinted.”

Katsuki stared. “What, the shit that baby ducklings do when they stare at you too long?”

“Well, that is one way to put it. It presents a little differently in humans, and is particularly more rare.” 

Katsuki remains silent, his eyebrows raised, waiting for her to continue.

“I didn’t plan on explaining this until after the diagnostic process was completed, but you seem like the type of person who wants to see the full picture,” she says, not unkindly. 

“Pretty much, yeah.”

She nods, a small smile back on her lips. “You see, for most animals, their developmental stage is very short when compared with humans. Cows and deer can walk on their own in a matter of hours. Wolves, a few days. Their child stage lasts only a few months to a year. Their relationships develop quicker, so it’s much easier for imprinting to occur, and less extreme. In humans, our development happens over the course of around fifteen years. For imprinting to occur, there must be a consistent social relationship that’s built over the course of almost all that time. With the human lifestyle, it’s rare for that kind of relationship to exist with anyone outside of your immediate family. For whatever reason, the imprinting bond isn’t seen between families. It’s typically a romantic bond, and more often than not, imprinted couples mate. Regardless of mating status however, these humans must maintain proximity to each other to remain happy and healthy. When your body has regulated itself over fifteen years or more to the presence of another person, it’s jarring to be separated. This is also why imprinting is so rare in humans - it’s an evolutionary nightmare. Understandably, most imprinted couples stay with each other because they want to.”

“So you’re saying that I imprinted on him?”

“I’m saying that it’s a strong possibility. And if that’s the case, the solution will be much easier than if something else is causing your symptoms. If you’ve imprinted, your symptoms will have been brought on by the unanticipated separation, and the solution would be to spend time with each other.”

“Yeah, that’s not gonna work.”

The doctor raised her eyebrows. “Is there a problem?”

“Well, I didn’t just leave him for a month after years out of nowhere. We’re not really…speaking right now. So I can’t just call him up to solve all my problems. And if I imprinted on him, why doesn’t he feel like shit too?”

“Omega hormones work differently. You operate on a much more intense cycle, where your heats come every few months. Alphas run through their cycle quicker, having a short rut of a few hours every two to three weeks. For omegas, heats can be debilitating. Their bodies tend to react the same way to a rejected imprinting.”

The phrase makes something stir uncomfortably in his chest. “Rejected?”

“If one party has imprinted on an uninterested party, it can be just as if not more debilitating than heat. But it’s constant. Thankfully, we’ve been able to find a solution for those cases. The best way to regulate their hormones is through mating. Making a stronger bond with someone else is enough to break the bond made by imprinting.”

“So if he doesn’t accept me, I’ll have to mate with someone?” Katsuki’s breath starts to go shallow. This is rapidly turning into a worst case scenario.

“If this is imprinting, and if it is with him, and if he rejects you. There’s a lot still up in the air, Bakugou-san, so I’d rather you not think too far ahead before we do these tests, alright? I promise that we’ll come up with a treatment plan once we have enough information to work with.”

Katsuki huffs. Asking him not to think about the prospect of his entire life being upended is pointless. But he supposes he doesn’t have to start drafting up plans yet. There’s still hope it’s some kind of hormonal imbalance. Maybe his suppressants are horribly off and had caused this. Maybe he has some sort of debilitating disease that won’t require either confessing his lifelong feelings or mating with a person other than Izuku. Or both of those things. Katsuki’s head throbs.

“You’re almost due for another round of medication, so I’ll send the nurse back in soon. I’ll order those tests for you and we’ll try to get those results by the end of the day, okay?”

Katsuki nods, only half present. His mind still floats in fog, giving everything a surreal quality that makes him doubt if it’s real. The nurses come and take his blood and poke and prod him some more. 

After a while his parents come to check on him, his mother her usual mixture of furious and worried. His father pushes the sweaty hair back from his face, and Katsuki pretends not to like it, but it’s soothing. It reminds him of being young, of being cared for as a sick child when his biggest worries were doing well on a test and making sure all his friends knew he was going to be number one. 

“It’ll be okay, Katsuki,” his father says, his fingers in his hair, and Katsuki tries to force down the knot in his throat. His mother lays out things they grabbed from his apartment - spare clothes, toiletries, a few books to pass the time. He kicks them out after a while, insisting that they don’t need to wait around with him while he waits for test results. He’ll know soon enough, and as much as he loves his parents, he doesn’t want them here when he finds out his fate. He’s done his fair amount of hospital time. He can handle it.

The rest of the day is quiet and a bit lonely. None of his friends know he’s back in the country, and he wants to keep it that way. He needs time to sort this shit out before it becomes everyone else's business too. 

Unfortunately, he’s not afforded that luxury. Around 3pm, his phone starts buzzing. He groans and picks it up from his bedside table, assuming it’s his mother. Katsuki jolts so hard he drops his phone onto the bedspread. A contact photo smiles up at him, with unruly green curls and green eyes scrunched into a grin.

He stares at the phone, unmoving. It goes to voicemail. It starts ringing again. Katsuki just sits and watches as texts start coming in, all from Izuku. He swallows hard and shuts his phone off. Izuku must have found out he’s in the hospital, or at least back in the country. Well, Katsuki certainly isn’t going to talk to him, not after a month of complete silence. 

Katsuki tries to read a book to calm down, which ends up working too well. The mixture of fading adrenaline, medications, and words on a page lull him into a half sleep state. Footsteps in the hallway, quick and loud, break him out of his stupor. He sits up groggily just as the door bangs open.

Izuku stands in the doorway, hair askew and suit ruffled. He must have just come from class. “Kacchan!”

Katsuki stares at him, anger simmering beneath his skin, burning away his exhaustion. “What. The fuck. Are you doing here?”

“I came as soon as I heard! I think your mom must have run into my mom because my mom called me right as I was getting off work. She asked if I’d talked to you recently, and I said no, and she said maybe I should because you were in the hospital. And good friends should always visit each other in the hospital. And I said that’s ridiculous Mom because if Kacchan was back in the county and in the hospital he would have told me! But you didn’t! And I had to make sure you were okay!”

The words fly out of Izuku in a rush, leaving him panting for air. Katsuki forces himself to take a deep breath. “Did you consider that maybe I didn’t tell you because it’s none of your fucking business?”

Izuku frowns. “Your health details are your business Kacchan, but I’d like to know when you're in the hospital. And when it’s so serious that you have to cut your mission abroad short! I know how important that was for you.”

Katsuki would have said fuck the mission if Izuku had just asked him to stay in Japan. But Izuku didn’t. “I’m fine, nerd. See? I’m all in one piece. You can go the fuck home.”

Izuku’s big green eyes fix on him. “But Kacchan, what happened? Were you hurt?”

Katsuki groans. “It’s just fuckin’ omega stuff! Issues with my hormones, okay? Like I said, none of your fuckin business.”

Izuku frowns. “You know you can tell me anything, Kacchan. You don’t have to do this on your own. I can help you.”

“I don’t need your help. What will your boyfriend think if he finds you fawning over me in the hospital, anyway? Go home, Izuku.”

Izuku’s mouth opens, his face a picture of shock. Katsuki feels his face go red. Why did I have to say it like that?

“We broke up, actually,” Izuku says.

It’s Katsuki’s turn to be shocked. Izuku isn’t known for long and healthy relationships, and sure he’s dated more people in the past few years than Katsuki can count on one hand, but he’d only started dating this guy a month before Katsuki left. That made it Izuku’s shortest venture to date. 

“The fuck did you break up with him for?”

“It doesn’t matter. We disagreed about some things and I wasn’t willing to change my mind. He basically gave me an ultimatum, so we broke up.”

Katsuki tries to ignore the flutter of his heart. He’s gotten his hopes up too many times after Izuku’s break ups. His omega always cheers, chanting this time, this time he’ll see that we’re the one he’s meant to be with. He’ll see that we’re made for him!

But without fail, Izuku always comes back a few weeks later with a new date, convinced this time they’re the one. Katsuki had started to see it as bullshit, but Izuku’s most recent relationship felt different. Izuku had never dated a guy before. When Izuku said he was bringing his new partner to their monthly friend hangout, Katsuki figured it would be another omega girl with stars in her eyes for the hero Deku. 

But when Katsuki arrived, it was a man Izuku had his arm around. A man Katsuki had never seen before, with big brown eyes and blond hair. And dimples. Ugh. 

Katsuki’s heart had sunk below the floorboards. Izuku had never dated a male omega before. Katsuki figured he was only into omega women, and even if some secret part of his heart always hoped he could be an exception, he’d largely accepted that Izuku couldn’t possibly love him, simply due to biology.

But Izuku had his arm around this male omega, and when he pressed a kiss against the man’s temple, Katsuki realized something worse. It wasn’t that Izuku didn’t want a male omega - no, Izuku just didn’t want Katsuki. It burned him from the inside out, the rejection making his omega internally shrivel up. He hated how sick it made him feel, how weak. He didn’t want his happiness to be reliant on Izuku’s dating whims. He didn’t want this constant back and forth anymore, the emotional ups and downs of believing for just a second that maybe he could have a chance.

So when Best Jeanist let him know about an exchange program abroad looking for experienced young heroes, Katsuki signed up before he could stop himself. It was the kind of opportunity he would have declined even a month prior, because the prospect of being away from Izuku for that long was unthinkable. Even when saving for Izuku’s suit, Katsuki stuck to domestic missions for the same reason.

But clearly Izuku didn’t feel the same way, so why should Katsuki? He deserved to be free and live his life outside of that burden. So he sent Izuku a text and got on a plane, determined that the next time he set foot in Japan, he wouldn’t be diseased with this clawing need for Izuku. He would find a way to move on, to cope. He needed his life back.

Clearly his body had other plans. If Dr. Hirata was right, he couldn’t even successfully wring Izuku out of himself. He was trapped to feel this way forever. The doctor's words float back up in his mind, the solution she said they present for rejected omegas. Mating with someone else is strong enough to break the imprinting bond.

The prospect churns in Katsuki’s stomach, making him nauseous and short of breath. Nope, no, he will not think about that yet. It won’t happen. He won’t let it.

“Good,” Katsuki says, unable to stop himself despite his better judgement. “He didn’t deserve you anyway.”

Izuku cocks his head. “Kacchan, what’s going on? You look terrible and you keep saying weird things and we haven’t talked in weeks, and -“

“Well, whose fault is that?” Katsuki snaps.

Izuku raises his eyebrows. “Yours? You told me to give you space, so that’s what I did.”

Fuck. Katsuki grinds his teeth together. Of course that’s how it looks from Izuku’s perspective. He wouldn’t see how he’s slowly sidelined Katsuki for months, pushed him away further and further. Katsuki thought that sending the text and fleeing the country was just saying the quiet part out loud. Izuku didn’t want him. Not as a mate, not as a boyfriend, and based off his recent behavior, not even as a friend. 

Katsuki was determined to win every fight. It was his driving principle. But after so many years, Katsuki thought that it might be time to forfeit this particular battle.

“You’d barely spoken to me for months. Just because I decided to fucking say something about it doesn’t make it my fault-“

“You didn’t say anything about it! You said that you didn’t want to talk anymore. So I believed you! I’ve fought against you for so many years, doing the opposite of what you say, that I thought, you know, how about just this once I actually do what Kacchan asks? Let’s see what happens when I actually go through with it.”

Izuku’s chest heaves, his face flush with anger. An emotion, not quite anger and not quite guilt, curdles in Katsuki’s gut. Stubbornly, hopelessly, he wants to say that Izuku is supposed to fight against everything he does. He expects it. He counts on it. Why did this time have to be different? Why was he so willing to cut off contact, without any pushback?

“I just thought you didn’t care,” Katsuki says coldly.

Izuku huffs again. “That’s shit Kacchan. You’re full of shit. And I don’t know where you got the idea that we’ve barely spoken for months from -“

“Like hell you don’t, you never texted or called me first! I always have to reach out to you! And I know that you’re busy, I understand, but it feels like shit when you can’t even tell me that and I just have to fill in the blanks on my own. And then to see you parade around your new girlfriend - oh, no, sorry, boyfriend - every week” - Katsuki holds back a growl - “Just really goes to show where your priorities are. So yeah, I’m not going to beg to split the attention of your fuckin flings or whatever the fuck they are. I thought we were more than that.”

The fury has melted from Izuku’s face. His eyes are round, and the faint sheen of tears has another wave of frustration rising in Katsuki. He’s about to keep going, to spill out the full truth, but a knock sounds from the other side of the door. The nurse steps in. “Sorry to interrupt, Bakugou-san. It’s time for your next round of tests.” She looks over at Izuku. “We’ll have to ask that you go back to the waiting room in the meantime.”

Katsuki locks eyes with Izuku one last time before he’s shaking his head and walking back out to the waiting room. 

Katsuki spaces out during most of the tests, moving his body as the doctors instruct and trying his best to ignore where they poke and prod. He has enough to think about. Izuku seemed shocked, even heartbroken to hear Katsuki’s feelings. It wasn’t that unusual - Izuku is a crier after all - but it seemed to run deeper than that. He replays his own words again and again, but finds that there’s probably nothing much he would have changed. If anything, he wants to say more. Now that the stream of truth has started, he wants to break the whole dam. Just get the whole disaster over with at once. Maybe if he finally manages to choke out that he’s in love with Izuku, his body will stop betraying him. Maybe then Izuku will actually leave him alone, and Katsuki will get to discover some depressing, Izuku-less sense of normal. 

Katsuki is left alone after the tests, and for the first time in a month, he soaks in the peace and quiet. No one must tell Izuku that he’s back in his room, since he doesn’t show up again. Maybe he left, finally calling it quits with Katsuki’s shit.

Towards the end of the day, the doctor comes back in. She’s holding a clipboard this time with a small stack of papers already attached.

“How was the rest of your day, Bakugou-san?”

“Fine. No complaints.” About anything to do with her at least. The staff here are decent. 

“I’m glad to hear it. I’m ready to discuss the results of the tests with you.”

Katsuki can only nod, anxiety filling his limbs.

“Your hormones are severely imbalanced, even with your suppressants. To re-regulate them using suppressants would require an absurdly large dose, the side effects of which keep it from being a viable solution.”

“So, the next question is, where is that imbalance coming from? It must have been triggered recently, since you’ve only now developed the more severe symptoms. This is the trajectory we took in deciding on this diagnosis. All your tests agree with a heavy hormone imbalance and a form of proximity illness. These symptoms indicate that you were separated from someone you spend a lot of your time around. Our bodies acclimate to external stimuli we encounter on a daily basis. When one of those stimuli is another person, our biological characteristics sync up with one another. Our pheromones calm each other, yes, but the benefits aren’t just mental. Physically, being around a loved one can reduce heart rate and blood pressure. Your hormones will even out, your cycles becoming more regular. When this is removed, your body has to learn to regulate on its own again. That can take months of adjusting. But these cases where the body cannot re-regulate is what we refer to as imprinting, because it speaks to a different and very specific type of bond. Bakugou-san, we confirmed that you have imprinted on someone, and that without their presence, your symptoms will continue to worsen.”

Katsuki’s heart sinks through the floor. He feels as though the world is falling away from him, fracturing into jagged pieces that don’t make sense together. He distantly recognizes that his breathing is heavy, his vision getting fuzzy at the edges.

“I know this is a lot to take in, Bakugou-san. Please take a deep breath. You do have options. I’m working with other experts to ensure we give you the best treatment possible. This isn’t permanent.”

Katsuki fumbles through the rising panic for anything to hold onto. The doctor’s voice is only on the fringes of his mind, barely heard over the alarm bells that scream in Katsuki’s head mate, mate, you’ll have to mate with someone. It won’t be Izuku. You have to mate with someone who isn’t Izuku.

“I have to mate with someone,” he manages to choke out.

Dr. Hirata looks at him with steady, sympathetic eyes. Like always, the look of sympathy prickles uncomfortably underneath his skin, but it’s drowned out by everything else. “That is the most effective solution, yes. If you can’t mate with the person that you’ve imprinted on, then we suggest mating with someone else in order to dissolve the imprinting bond. Earlier, I mentioned that in some cases, spending time with the person you’ve imprinted upon is enough. Unfortunately in your case, your hormones are so dysregulated I don’t think that’s an option. You’ve been on suppressants for so long so consistently that your body has largely forgotten how to do any regulating on its own. Even if you hadn’t imprinted upon someone, you would likely be experiencing severe issues anyway. Which is why I imagine you were put on suppressants at such a young age in the first place.”

She’s right. After his first heat at fifteen, Katsuki immediately begged his parents to get him put on suppressants. It had been horrific. The pain was excruciating, extending past his abdomen through his whole body. It lasted for ten days, double the average heat length. He had to skip school the whole time, and as a training hero he couldn’t afford to miss a week or more of school every few months. So he got rid of it. He took as much suppressants as necessary to reduce the pain, and eventually enough to get rid of the heats entirely. He knew he required more than the average omega. Maybe that’s because he had unknowingly imprinted on someone, maybe it’s just the way his body is. Either way, it’s coming back to bite him in the ass now. 

Katsuki’s head falls into his hands. He doesn’t have anything else to say to the doctor, so they sit there in silence until she stands. “I’ll give you a few minutes to process. Feel free to call me back if you have any other questions.”

She goes to reach for the door when it bangs open. Izuku stands in the doorway, huffing and disheveled once more, just as he had been a few hours previously. “Kacchan! Are you okay? The tests have been taking really long and they keep trying to kick me out saying visiting hours are over but I need to make sure you’re okay-“

A nurse appears behind him. “Sir, you really are not allowed back here without proper permission. I have to ask you to leave.”

The doctor looks between Katsuki and Izuku. She raises an eyebrow at Katsuki, and he nods. “It’s alright. Bakugou-san has just received some big news, so I’m sure he’d like to speak with him. If anyone has problems with it, you can send them to me.”

Izuku barrels in, not needing to be told twice. The doctors leave, and Katsuki now has no buffer between the information bomb he was just given and Izuku’s prying eyes. 

“What did she mean, big news? Did you get a diagnosis?”

“Something like that,” Katsuki says. 

Izuku sits on the chair beside his bed. “Well? What is it?”

Katsuki stares until Izuku’s face goes red. “What’s wrong with me, I’m sorry, Kacchan. I know it’s your medical business, I’m just so concerned and need to know if you’re okay but I understand if it’s personal-“

“Stop freaking out, nerd.”

Izuku gives him a grateful look, and for a moment it’s so similar to how they used to be that Katsuki burns with the memory.

“I…” he tries to get the words out, but none come to him. How does he explain this? “My hormones are all fucked.” Izuku nods, waiting for him to continue.

“They’re so fucked that I can’t regulate them on my own, and not even suppressants will help.”

“Then what can you do?”

Katsuki opens and closes his mouth. The silence stretches between them. Izuku leans forward with his elbows on his knees, his fingers steepled beneath his chin. His eyes are glued to Katsuki, as if he’s the only person in the world.

“I have to mate with someone.”

The words come out soft. At first, Katsuki doesn’t think Izuku heard him, because he doesn’t react. But then he leans back. “Oh.”

“Yeah, oh.”

Izuku’s brow furrows, and Katsuki can practically hear the gears of his brain turning, trying to calculate a solution. “Okay. Well. Who do you want to mate with then?”

“I don’t fucking know! I just found out about this five fucking minutes ago! I don’t want to have to mate with anyone, but I guess I don’t get a fucking choice. And don’t give me that sad look.”

Izuku’s eyes had started to widen and were well on their way to Kacchan’s hurt, let me help Kacchan territory. He thankfully resumes his pragmatic look.

“It’s going to be okay, Kacchan. You have so many people who care about you who’d be willing to help. I’m sure any of your friends would be-“

“I’m not gonna mate with any of those clowns,” Katsuki growls. He’d rather live in pain forever than experience the humiliation ritual of going from friend to friend and begging them to sign themselves away to him forever. They don’t deserve that. Just because Katsuki doesn’t get to mate for love doesn’t mean he wants to subject anyone else to the same fate.

The reality of the situation begins to dawn on him. He will have to mate with someone. He won’t ever get to be Izuku’s omega. He’ll have to mate someone else, and maybe he’ll learn to care for them, maybe even love them, but it would always be a shadow of what could have been. His true feelings for Izuku will never die, even if the imprinting bond is no longer there. 

“I don’t give a shit if they’d be happy to help, they don’t deserve that. And if I tell them I need it for my health, they’d do it without a second thought.”

“Of course we would! Of course we’d do anything to keep you safe!”

We. Katsuki’s heart hammers in his chest. Izuku falls silent and looks away. 

“Kacchan…I’m going to say something. And I want you to take it seriously. I want you to actually think about it before you respond. Can you do that for me?”

Katsuki doesn’t think Izuku means to let a bit of his alpha creep into his voice, but it’s there all the same. A ripple of dominance courses through Katsuki, and while it’s not enough to force him to submit, he has to physically resist from baring his neck. Instead, he nods.

Izuku takes a deep breath. “I think we should mate.”

Katsuki immediately opens his mouth to say are you fucking crazy you deranged nerd, but one look from Izuku and his mouth is clamping shut again. He can’t be serious. But Izuku looks deadly serious, that all too familiar dead set look in his eye he only gets when he’s determined to get his way.

“I meant it when I said I’d do anything for you, Kacchan. This included.” Izuku wraps his hands around Katsuki’s. A shiver races up his spine. Izuku’s eyes never leave his when he says, “I’ve always known I wanted to spend the rest of our lives together in some capacity. Is this really that different? For guaranteeing your well being, it’s a small price to pay.”

When Katsuki doesn’t speak, Izuku continues, sounding less sure of himself. “And I understand if you don’t want me. It’s a big commitment, a lifetime commitment, and I know you just asked for space but I want to do this for you. If you’ll have me.”

Tears build in Katsuki’s eyes, making his throat tight. Izuku is offering his biggest desire on a silver platter. After years of aching and pining just…offering. As if it had been an option the whole time. “Izuku,” Katsuki starts but his voice breaks off wetly. “I can’t do that to you.”

“Kacchan, are you crying?”

“Of course I’m fuckin crying! You just offered to mate me, you dumbass! I can’t - I can’t ask that of you, it’s so fucked.”

Izuku’s eyes are hard as steel when he says, “You’re not asking it of me. I’m offering. If anything, I’m asking you. Because I care about you, Kacchan. And I don’t trust anyone better than myself to take care of you.”

Katsuki pulls his hands away to press his palms into his eyes hard enough to make stars dance behind his eyelids. Just think about it, a voice whispers to him. Why shouldn’t you say yes?

Because this wasn’t how this was supposed to go, that’s why. He loves Izuku, has wanted him since he knew what wanting felt like, but not when it feels like coercion. Not when it’s against Izuku’s will.

But it isn’t against his will, the voice says. He’s offering the perfect solution. You’ll get your health back. You can keep your job. You get to be mated to the love of your life. Isn’t this the best case scenario?

Guilt churns in Katsuki’s gut. When Katsuki opens his eyes, Izuku is looking at him with a small, hopeful smile. “Please, Kacchan,” he says. “I want this.”

I’m going to hell for this. Satan himself is going to create a tenth circle of hell just for me because of all the shit I’ve put Midoriya Izuku through.

Katsuki nods. “Okay. Let’s do it. Let’s mate, Izuku.”

Izuku tackles him into the bed with a hug. Katsuki lets out a surprised oof but wraps his arms around Izuku. “You’re gonna be okay, Kacchan. You really scared me,” he mumbled against Katsuki’s neck.

“No need to be worried, nerd. Some fuckin hormones aren’t gonna be what takes me out.”

Once Izuku detaches himself from Katsuki and Katsuki inconspicuously wipes away his tears, he calls the doctor back in. It’s getting late - surely she should have already left by now, but she’s still here. She’d given them the time they needed to process and sort out the next steps.

“We’ve decided to mate,” Katsuki says, the words feeling foreign on his tongue. Dr. Hirata nods and a small smile plays at the corner of her mouth. 

“Thank you for letting me know, Bakugou-san. This will be a transition period, so the team is here to help you through this difficult time. We’ll debrief the both of you on what to expect in the coming days and what your care will look like. For now, I’m sure you’re exhausted from all the tests today. I’ll leave you to get some rest. And unfortunately Midoriya-san, I will have to ask you to leave for good this time.”

Izuku shoots a concerned look at Katsuki. “Get the fuck out of here,” Katsuki says. “I’ll be fine until morning.”

Izuku nods, gives Katsuki’s hand one last squeeze, and leaves with the doctor. Katsuki is left alone in his room, the only sounds the whir of the air conditioner and the occasional rumble of traffic on the street below. He’s restless for a few hours, alternating between eating dinner, attempting to watch tv (which only lasts for twenty minutes), and spiraling into existential dread about the rest of his life. Despite it all, the events of the day do catch up to him, and he drifts to sleep.

~~~

When Katsuki wakes up, morning light streams in through the window and Izuku is already at his bedside. “Morning, Kacchan!”

“The fuck are you doing here already? Don’t you have work or some shit?” Katsuki asks, rubbing the sleep out of his eyes.

“I wanted to see you. And I wanted to be here when the doctor tells us what comes next.”

All at once, the reality of the past twenty four hours comes crashing down on Katsuki. “Fuck.”

Izuku moves right along. “She’ll be here in a bit. The guy at the front desk told me she gets in at eight. I got you some breakfast too!” He gestures to a takeout container waiting on his bedside table.

Christ. Leave it to Izuku to barge into a hospital and act like he owns the place. Is there anyone he can’t be instant friends with? Irritation prickles at the back of Katsuki’s mind, bringing the urge to snap that he doesn’t need Izuku here, that he has it under control. Izuku’s big green eyes look at him with hope and sympathy, but all Katsuki can see is his arm around that fucking omega man he dated for all of a month. And now he agreed to mate? It doesn’t make any fucking sense.

Instead, Katsuki holds it in. He’s got enough shit to deal with for now. He sits up and grumbles his thanks. 

A few minutes into his shared breakfast, Dr. Hirata comes in. She gives them a basic run down of what the next two weeks of Katsuki’s life will look like. He can’t be on suppressants when he mates, since the whole point is to fix his hormones. His last dose was the day before, and once the last of it is out of his system, his heat will start. They have roughly eight more hours.

“Get all your affairs in order,” she says. “There’s no telling how long this heat will last. Hopefully, your body will react positively to the mating and the worse of the effects will be decreased. But regardless, you’ll need to be taken care of for up to two weeks. Midoriya-san, will you be able to do that?”

Izuku nods eagerly. “Of course. I’ve already called off work.”

Katsuki looks at him in surprise. He just can’t get over how eager Izuku is.

“Great. Then Bakugou-san, once we administer your last round of medication, you’re free to go. You’ll be more comfortable at home for this process, and you’re stable enough to leave. I recommend you two spend these next few hours preparing everything you’ll need for the coming weeks.”

With a final wave and a demand to call if they had any questions or his symptoms returned, she leaves. Izuku bursts into explaining his plan for the day. “We’re going to go to the store first. I already started making a list, but I’m sure there’s plenty I’m forgetting. I’ve already got slick pads, heating pads, spare sheets, pain killers - though I guess you’re being prescribed some so you probably don’t need those, good to have anyway though - some basic snacks, but I wanted to meal prep as well because you can’t live off cup ramen for two weeks and we won’t be cooking, so-“

“Izuku."

“What meal do you think would be best? I know you like spicy but it should be something mild since you’re sick-“

“Izuku!”

Izuku finally breaks from his ramble. “Yes, Kacchan?”

“What. the fuck.” Katsuki groans. Izuku cocks his head. “How have you already thought of all this?”

“I’m going to be your alpha, Kacchan. I need to be able to provide for you.”

Katsuki doesn’t know if he’s going to pass out or throw up. This is all happening so fast.

“Okay. Let’s go to the store.”

Izuku grins and shoots up. Katsuki glares as he says, “But we’re not buying slick pads. They’re uncomfortable as fuck. Make me feel like I'm wearing a damn diaper. So put however many towels you think we’ll need on your nerd list.”

Izuku just grins.

~~~

Izuku buys entirely way too much shit. He’s also enjoying himself way too much. He can’t keep stop smiling as he walks down each aisle, pointing at different items and asking are you sure we don’t need this, kKacchan?

They don’t need two different kinds of probiotics. Katsuki doesn’t even think he needs probiotics. He’s had enough medication for a lifetime. Shopping with Izuku is a public humiliation ritual, but he just keeps saying yes to make sure all their bases are covered. Whatever.

When they check out, Izuku is pushing a nearly full cart. It overflows with towels, sheets, blankets, enough groceries to feed a small army for a month, and a plushy that Izuku insisted on. You need good nesting materials! He’d said. Katsuki hadn’t nested once in his entire life. He'd be damned if he was going to start now. 

As they shopped, Katsuki could feel an itch starting underneath his skin. Then, a thin sheen of sweat and occasional chills. The telltale signs of heat are staring, and it will be in full swing in a matter of hours. The arousal hasn’t started yet, but he can feel its impending presence. He wants to be closer to Izuku, to keep a hand on him at all times and fill his lungs with his scent.

Izuku insists on bringing their haul inside Katsuki’s apartment by himself. He sits Katsuki down and tells him to make himself comfortable. Katsuki instead puts everything away as Izuku brings it in, because he’ll be damned if things get put where they didn’t belong. He has a very specific organizational system, and medical emergencies be damned, it will stay that way.

Once their haul is sorted, Izuku has to leave to grab clothes from his own apartment. “I‘ll be as quick as I can,” he says, pulling on his shoes. “I should be back in an hour, and your heat shouldn’t start fully for another three.” He squeezes Katsuki on the shoulder before leaving. For an awkward moment, he looks like he wants to do more, but Katsuki turns away. He doesn’t need Izuku giving him affection just because he thinks he owes it as his future alpha. 

Izuku’s absence leaves Katsuki to face his empty apartment that’s been uninhabited for over a month. The smell of disuse and dust hangs heavy in the air. It itches. He begins cleaning, starting with basic things like wiping off the surfaces and sweeping the floor. He gravitates towards his bedroom, the place he and Izuku will be spending most of the next few weeks. It’s as neat as he left it - the bed sheet is tucked tight, his desk is spotless, and his nightstand is empty albeit dusty. But something isn’t right. 

What had once seemed comforting to Katsuki - the precise cleanliness, the sharp edges - suddenly feels cold and clinical. He wants it to feel warm, inviting. His alpha is going to mate him here. It has to be perfect.

He tugs up the old sheets, replacing them with the ones Izuku purchased earlier that day. They’re softer, Katsuki notices. He’s never noticed the softness of sheets before. It makes a difference. The comforter is replaced by a pile of blankets, a mixture of his own and the new ones. He smiles as his scent spreads to the new items, making the room smell like him. There’s a trace of Izuku’s scent buried in the sheets.

Katsuki tries a few different configurations - the blankets laid out next to one another like a patchwork quilt, then the blankets bunched all around the perimeter of the bed to form a wall of sorts. Each time, Katsuki rips the blankets away in frustration. His bed is in the center of the room, with only the headboard against the wall. The nest is falling off the sides, and eventually, the blankets would get kicked off. This needs to last. 

He pushes the bed frame up against the wall so that it nestles into a corner. He builds the cocoon of blankets up again. Yes, he thinks. This time it’s perfect. The best goddamn nest anyone’s ever seen-

“Kacchan, I’m home!”

Katsuki jolts out of the strange trance he’d been sucked into. He stares down at the last blanket in his hands and the perfectly formed nest that is now dominating his bed. 

“Kac- oh. Oh, wow.” Izuku’s stunned voice comes from behind him. “You told me you didn’t nest.”

“Shut the fuck up! I’m not nesting, I'm just -“ Katsuki flails around the blanket he was holding. “Goddammit.”

Izuku’s face goes red as he tries to hold back a laugh. “Oh, Kacchan, it’s okay. This is good! It means your heat is starting. And you made us such a lovely nest.”

Katsuki wishes he could burn into flames. His face is so hot he thinks he might be halfway there already.

“It’s not finished yet,” he grumbles. “It’s missing something.”

Izuku’s face falls. “Did we forget something at the store? There’s still probably enough time-“

Katsuki stomps over to Izuku and begins tugging on his hoodie. It’s a large ancient thing, a relic from their UA days - sweaters they all got in commemoration of their third year sports festival. Katsuki blew his up on accident years ago. It happens more than he’d like to admit with his clothes, but he particularly mourned that hoodie because it was so goddamn comfortable. “Come on, off with it.”

“Ack, what are you-“

Katsuki yanks the hoodie from Izuku’s head and tosses it towards the bed. He runs it along the walls of blankets, spreading Izuku’s pine forest scent into the mix. Then, he pulls the hoodie over his own shirt. Izuku’s scent fills his lungs, drowning out any remaining trace of dust.

“Now it’s done.”

Izuku stares at him with wide eyes and parted lips. “Uh.”

“Got everything you needed from your house?”

Izuku nods, apparently still lost for words.

“Let's finish getting ready then.”

They spend the next hour prepping meals and snacks for the rest of the week. Izuku prefills water bottles with electrolytes and keeps a pot of curry simmering on the stove. He portions out the rice and curry into containers to be frozen and periodically taken out over the two weeks. There was a pile of ramen, protein bars, protein shakes, apples. All things either easily cooked or easily eaten.

Katsuki is forced to sit and watch most of the time, Izuku still deeming he needs to rest and to let him take care of it. With each passing moment, Katsuki’s senses became progressively heightened. He can feel every thread of fabric touching his skin, and in seconds he alternates between being too cold and too hot. Breathing in Izuku’s scent is the only thing that keeping him balanced. 

Eventually, he decides it’s time to stop beating around the bush. Izuku just finished the last of the preparation and is wiping down the kitchen. The smell of cleaner makes Katsuki’s noise wrinkle, but he keeps it to himself. 

“I’m going to go lay down.”

“Okay, Kacchan! I’ll be there in a second.”

Katsuki approaches his unrecognizable bed. The nest he made still evokes a deep satisfaction, but it all feels so foreign. The reality of the situation is starting to crush him. In a few minutes, Izuku will be in here. He will join him in his bed, and they will mate. 

He is going to have sex with Izuku. Holy fucking shit.

He lays down in the nest and covers himself with his favorite blanket, hoping it will make him feel less vulnerable. It doesn’t really work. Tears burn at the back of his throat, but Katsuki holds it in. He can’t afford to break down now. This is his life now; he has to live with it.

Izuku cracks open the door and peaks inside. “Can I come in?”

“Course you fuckin’ can.”

Izuku approaches the bed, eyeing it cautiously. “Just get in here already,” Katsuki says, holding up a blanket as an invitation. Izuku climbs in, but Katsuki notices he’s holding a laptop. “I thought we could just watch a movie for now. No need to jump right into things, right?”

An angry part of Katsuki snarls that Izuku just wants to delay the inevitable. Another part of himself, the one he chooses to listen to, thinks thank god. He doesn’t know where to begin with this. Are they just supposed to start kissing? Is kissing off limits? This isn’t meant to be romantic, but Katsuki doesn’t know if he’s capable of non romantic sex. A movie, at least, is much less intimidating.

Izuku props up the laptop against his knees and lifts his arm. Katsuki stares, not knowing what it means. “Will you come here?” Izuku gives his arm an impatient wiggle. Katsuki’s stomach flips, but he nestles into the crook of his shoulder. Izuku’s calming scent fills his lungs, burning in the back of his throat. Katsuki doesn’t think his heat has started yet - he doesn’t feel too different. But then he has to consciously resist pressing his nose in closer to get more of Izuku’s scent, and yeah, okay, maybe something is different.

Izuku opens his laptop, his fingers trembling just slightly as they move over the keys.  He already pulled up the movie - All Might: Origins. It’s not Katsuki’s favorite All Might movie – it’s a bit too slow for his liking, and pales in comparison to the other two movies in the trilogy. Katsuki snorts. “Seriously?”

Izuku glances down at him. “You want something else?”

“No, no it’s okay. Fitting, I guess. All Might’s gonna freak when he finds out about us. Kinda funny how things work out.”

Izuku smiles. “I think he’ll be happy! We’ll have to take him out somewhere special to tell him.”

“Ugh, fuckkkk,” Katsuki groans.

“What’s wrong?”

“We’re gonna have to tell people.”

Izuku’s eyes get wide. “Don’t worry about that now. We have to get through the next two weeks first.”

Katsuki frowns but doesn’t press it. “Fine,” he grumbles. Despite Katsuki’s accusations of the movie being a corny choice, it’s somehow perfect. He’s seen it enough times that each scene is familiar and lulls him into a sense of comfort. 

About twenty minutes in, Izuku’s fingers start to skim up and down Katsuki’s arm. Izuku’s eyes don’t leave the screen, so Katsuki doesn’t react either, instead focusing on soaking up the attention. Shivers course through him, his over sensitive skin making every sensation vibrate through his entire body.

Izuku’s fingers move to his hair, his blunt nails scratching at his scalp. A rumble starts in Katsuki’s chest, a deep vibration that takes him by surprise. Izuku finally looks at him. The room is dark except for the computer screen which lights Izuku’s face a luminescent blue-green. His lips quirk up in a smile. “Are you purring, Kacchan?”

Katsuki rolls his eyes and looks away. It’s not like he can help that it feels nice. He hasn’t had any physical affection in a month for fuck’s sake! 

Izuku doesn’t press it, instead continuing to curl his nails into Katsuki’s scalp. Katsuki’s eyelids slip closed, and he lets himself float in the sensation. It zips up and down his spine, filling him with heat. God, he wants Izuku to keep touching him, to run his hands all down his body -

Katsuki jerks away, startled by his own thoughts.

“Everything okay?” Izuku asks with wide worried eyes.

Katsuki can actively feel his inhibitions slipping away. Every other thought is interrupted by some revelation about Izuku - how bright his eyes are in the dark, how thick his scent is as it seeps into the nest, how well the deepness of the pine mixes with the sweet musk of Katsuki’s own scent.

“It’s starting,” he says. 

“Okay,” Izuku replies softly. “Just lay back down, okay? We’ll keep watching the movie for now. Let me take care of you. Try not to worry.”

His anxiety spikes, sending his heart racing. “Wait, Izuku, shouldn’t we fuckin, I don’t know, talk about this? Talk about what we’re comfortable with? What’s going to happen?”

“We’ll, we’re going to have sex.” Izuku says it so plainly. I’m not going to survive this, Katsuki thinks distantly. This is how I die.

Izuku looks like he’s trying to hold back a smile, but he continues matter of factly. “And we’re going to mate. And in terms of what we’re comfortable with, I’m not the one in the vulnerable position here. There’s nothing you could do that I wouldn’t like. My priority is just to take care of you. So what do you want?”

Everything, Katsuki thinks selfishly. I want it all. 

The worst part is, he’s allowed to ask for it. After years of pain and yearning, he can simply ask for what he wants and receive it. No dragging it out of Izuku with punches and desperation. Just them, together, in this nest Katsuki built and the knowledge of what’s about to happen. 

Katsuki takes a deep breath. “I want you to kiss me.”

Izuku’s eyes widen just a fraction and his lips part slightly. Izuku reaches out a hand, cupping the side of Katsuki’s face. His thumb presses against the swell of Katsuki’s lower lip. “Okay, Kacchan. I can do that.”

Katsuki doesn’t breathe as Izuku leans in. The kiss is just the barest brush of lips. It’s dry and gentle and nothing like the erotica fest that Katsuki had imagined their first kiss being so many times. Gentleness isn’t their style - they’re much more for sweat and blood and grinding each other into the pavement until one of them submits. Katsuki thinks maybe this would be easier if it was the same way, if he was being forced to submit. Instead, as Izuku presses his lips against Katsuki’s again, still gentle but more insistent, Katsuki realizes that this isn’t a competition, but a journey they’re going on together. Izuku is taking his hand and leading him to the next step with care. 

Tears burn the back of Katsuki’s eyes. Izuku cradles Katsuki’s face as he kisses him lazily and chastely, not demanding any more than he’s willing to give. Izuku pulls away, and Katsuki chases after his lips. “Was that okay?”

Katsuki can only nod. “Good,” Izuku says, and heat courses through Katsuki. “Lay down with me.” Izuku opens his arm again, the damn laptop still open with the movie paused. Katsuki resumes his previous position, unsure of what Izuku is doing. Shouldn’t they keep going?

But he forces himself to turn his brain off, to trust that Izuku will take care of him. Izuku unpauses the movie. Katsuki tries to focus, but what started as an itch underneath his skin is beginning to migrate. He needs to kiss Izuku again. He needs to be touched so badly it aches -

Izuku runs his fingers down Katsuki’s body again, except this time he finds his way under Katsuki’s shirt. The sensation of their bare skin touching has Katsuki’s breath hitching in his chest. He forces himself to stay still, to not react as Izuku explores his body.

Izuku keeps a steady rhythm, back and forth from Katsuki’s scalp all the way down to his waistband. It goes like that for a few minutes, until Katsuki is forcing himself to not squirm, to not preen under Izuku’s hands, desperate for more touch. Finally, Izuku breaks his rhythm to wrap his hand around Katsuki’s thigh. He yanks Katsuki’s leg up until it’s laid across his lap, and his leg slots right in between Katsuki’s. Just the lightest pressure from Izuku’s thigh on his cock has Katsuki rutting forward, chasing the sensation.

Oh god, oh fuck, he thinks. He can’t fucking do this. If he can’t handle humping Izuku’s thigh without hyperventilating, he has no idea how he’s going to survive having sex with him. He buries his face in Izuku’s chest and almost forces his hips away, but Izuku’s hand comes back to his thigh and pulls him closer. He shoves his thigh further into Katsuki’s crotch, and Katsuki moans into Izuku’s shirt. 

Izuku’s hand rocks his hips back and forth until Katsuki is full on humping his leg. The embarrassment is drowned out by how delicious the pressure is. His overwhelming desire builds by the second, accompanied by hazy, jumbled thoughts of fuck, that feels so good and I can’t believe this is happening and more, more, please more.

“That’s it, Kacchan,” Izuku mutters. “You can let go, I’ve got you.”

A distant part of Katsuki is screaming to do anything but give in, but Izuku’s rough, scarred hands feel so good against his feverish skin. And isn’t this what he wanted anyway? What’s the point in resisting something he’s wanted for so long?

Izuku slips his hand under Katsuki’s waistband to grab a handful of his ass. Katsuki lets out a moan, a broken sound he didn’t even realize he was capable of making. Through the haze, he manages to break away for a moment.

Fuck this, Katsuki thinks. Fuck all of it. Fuck the doctors, fuck his stupid ass hormones, fuck every person Izuku’s had before him. If he’s going to be forced to get exactly what he’s wanted for ten goddamn years, he’s going to do it his way. And he’s going to love every fucking second of it because what’s the point if he doesn’t let himself enjoy it?

He slams the laptop closed and shoves it off the bed. Izuku glances down in alarm as it clatters to the floor. “Kaccha-” 

Katsuki climbs on top of Izuku and grips his face in his hand, his fingers digging into the meat of Izuku’s cheek. “I need you to kiss me,” he growls. He grinds his hips down and can feel the swell of Izuku’s dick against his ass, accompanied by the foreign pulse of his slick from his own hole. “I need you to mean it.”

Izuku’s eyes are blown wide, his hands automatically taking hold of Katsuki’s waist. His scent thickens by the second, flooding the room with the smell of arousal. “Of course. Anything, Kacchan, anything -”

“Izuku. If we’re doing this, we can’t do it halfway. I need you to be one hundred percent with me. I’m not going to hold back. And I swear to god if you hold back on me -“

Izuku’s eyes light with determination, so similar to how he looks at the start of a fight. A hand wraps around the back of Katsuki’s neck, bringing him down into a searing, open mouthed kiss. Where their first kiss was sweet and reluctant, this kiss is intense and all consuming. Izuku’s tongue swipes across his lips, and Katsuki opens for him until their tongues brush against each other. Katsuki groans into Izuku’s mouth and rutts down without even thinking about it. Underneath him, Izuku’s cock has grown to full hardness. 

It’s all so much. Katsuki has barely kissed anyone before, much less made out or hooked up, whatever hooking up is supposed to entail. And yes, it’s unhinged that his first time having sex is going to be when he mates like he’s some kind of old fashioned virgin saving it for marriage. Fucking christ. 

Katsuki had never put much stock in any of it - kissing, sex, heats. He didn’t see the appeal, since he always had something more important to focus on, and the one person he might have been interested in was off limits. But now Izuku’s tongue is in his mouth and currently learning the shape of his teeth, and Katsuki thinks he might come in his pants because it’s the most incredible thing he’s ever felt.

When Izuku finally breaks their kiss, Katsuki’s panting for air. “How’s that for one hundred percent, huh?” Izuku says. He’s got a crooked, self satisfied smile that Katsuki would punch off his face if he wasn’t so desperate to kiss him again. “I’d never give anything less than my best for you, Kacchan.”

Katsuki swallows hard. “Fine. Okay. I believe you.”

Izuku kisses down Katsuki’s throat as he speaks. He noses along his scent gland, the one that is destined to have a bite in it by the end of the night. Katsuki’s breath hitches as Izuku laps at it, licking up the pheromones and sweat straight from the source. Izuku groans into Katsuki’s neck and grinds up against him. Katsuki sees stars and he just doesn’t understand how people do this. Isn’t it too much? Every move Katsuki makes spurs Izuku on, which makes Izuku only kiss Katsuki harder. It creates an endless feedback loop of pleasure that has Katsuki’s heat addled brain turning to mush.

The worst part is, he isn’t even sure what to do next. When do they start taking off clothes? When should he start touching Izuku? Should he touch himself? Katsuki hates feeling out of his depth. It’s just sex, and he’s a fucking ace at practically anything he tries so this should be no different. 

“You’re thinking too much,” Izuku mumbles against his skin.

“The fuck do you know?”

“You got quiet. Stopped reacting as much. Just let me take care of you, Kacchan. Let me make you feel good.”

And oh, does that send shivers down his spine. The heat has reached him full force now; a feverish tingle spreads through his whole body and his abdomen cramps painfully. An emptiness aches within him, a soul-deep need to have something inside him that’s been left unattended for far too long. His baser instincts, usually quiet to the point of nonexistence, infiltrate his mind with chants of please alpha please, please fill me up, mate me, breed me-

Izuku flips their positions, laying Katsuki down on the bed. He takes his time admiring Katsuki’s body with burning glances and kisses that he traces from Katsuki’s jaw all the way down to the waistband of his shorts. A last valiant effort of nerves rise up within Katsuki to say I’m not ready yet I need more time, but Izuku makes his way back up without needing to be told. He sucks at Katsuki’s neck, and what had felt foreign and vaguely frightening the first time he did it a few moments ago now only elicits pleasure. Katsuki jolts in surprise as Izuku sucks his earlobe into his mouth, his teeth scraping the sensitive skin. “What the fuck - nghh.”

Why the fuck does that feel so good? And how does Izuku know to do that? Izuku chuckles against his skin, lapping and sucking harder as more moans spill from Katsuki. Katsuki couldn’t stop if he tried. He’s so hard now it’s almost painful, and the need to be filled is becoming unbearable.

“Izu- Izuku,” he manages to choke out.

“Hmm?”

“I need- fuck -“ another moan “- please, I need-“

“Kacchan, you need to tell me. What do you need? I’ll give you anything, baby.”

Katsuki whines. He can’t string more than three words of a thought together, much less say them out loud. Instead, he grabs Izuku’s hand and brings it down to his crotch, where the hard outline of his cock is visible through his shorts next to the wet spots where slick had seeped through the fabric.

“You’re ready for more?"

Katsuki nods. If he doesn’t get something inside of him in the next ten seconds his body might actually combust.

Izuku strokes him over the shorts and just that is enough to have Katsuki throwing his head back into the pillows. ”You’re so sexy like this,” Izuku mutters, his hand setting a tantalizingly slow pace over his shorts.

Katsuki lets out another impatient noise that has Izuku chuckling. “Okay, okay. I get it.” Izuku finally, finally slips his hand down into Katsuki’s shorts. He ignores Katsuki’s cock, instead smearing his fingers in the mess of slick that had already pooled in his boxers. Izuku spreads it over the length of his cock, making the slide smooth and velvety. Izuku’s hand is almost big enough to hold his cock entirely — as a male omega, he has both a cunt and a dick, but the latter was much smaller than his alpha counterparts. Izuku barely has to move his wrist to encapsulate Katsuki’s length, and each subtle squeeze has him choking on his own breath.

With his other hand, Izuku brings a finger to his entrance, barely teasing with the tip. When it finally breaches him, Katsuki lets out a relieved sigh. It’s practically nothing, especially with how wet he is, but when Izuku curls his finger inside, Katsuki feels a wave of satisfaction at finally not being empty.

“Another, c’mon,” Katsuki urges.

Izuku tsks. “Slow, Kacchan. Let yourself feel it. I promise I’ll take good care of you.” He tugs Katsuki’s boxers from his hips and off his legs, and Katsuki’s face burns as Izuku nudges his legs apart. Izuku kneels on the mattress between his knees, a mischievous look on his face as he pumps his one finger in and out so slowly. With no warning, Izuku licks a broad stripe up Katsuki’s length. Katsuki’s heart stutters wildly in his chest, his fingers flying to Izuku’s hair.

Izuku takes him fully into his mouth, and Katsuki has to physically resist thrusting up into the tight, wet heat. Izuku’s eyes never leeave his except for when they flutter closed as Katsuki slides down his throat. Izuku keeps him there for a few seconds before breaking off with a gasping breath. 

“How the fuck did you do that?” Katsuki asks hoarsely.

Izuku grins. “I might have a little practice. But you’re the perfect size, Kacchan. Makes it easier.” Izuku takes Katsuki into his mouth again, this time sinking all the way down immediately. Katsuki tries to be mad about the fact that Izuku got practice with someone else but then Izuku’s throat flutters around the tip of his cock and all rational thought flees his brain.

“You gotta stop, I’m close - fuck!”

Izuku sinks two fingers into Katsuki’s cunt, and the double stimulation has Katsuki’s thighs cinching closed around Izuku’s head. Izuku forces one thigh down with this free hand but doesn’t slow his pace, thrusting his fingers in and out in time with bobbing up and down on his cock. Pleasure courses through Katsuki, the sweet relief of being touched during heat making it all the more overwhelming. 

Izuku curls his fingers upwards at just the right angle, and Katsuki comes down his throat, every muscle in his body clenching tight. Izuku keeps going, slowly massaging with his fingers until Katsuki sees stars and weakly shoves him off.

“What the fuck, Izuku,” he pants.

Izuku hums and presses a kiss to Katsuki’s knee. “Was that good? Did Kacchan like it?”

“Fuck me. What the fuck.”

“Just did.”

“C’mere.” Katsuki makes a grabbing gesture with his hands, mind too muddled to be embarrassed. Izuku settles next to him, nuzzling into Katsuki’s neck. “I think I already smell enough like you.”

“That was just because I can.”

Katsuki laughs softly. “What the fuck was up with that? Made me come and we ain’t even mate.”

“S’not the point,” Izuku says into his skin. “We know it’s going to happen, so we can take our time. You’ll be begging for more in a few more minutes anyway.”

“Yeah, right. You sucked me dry, you freak.” Katsuki thinks Izuku might be right though. The satisfaction he felt from the orgasm is already starting to feel surface level and the ache in his abdomen is returning.

“So, you did like it then.”

“Course I liked it. Felt fuckin’ amazing.”

Silence falls between them for a moment, and Katsuki takes a second to soak it in. Street light streams in through a gap in the curtains, painting the room blue and stretching the shadows of the furniture. Everything is shrouded in darkness except Izuku, who’s pressed so close to him Katsuki would have to have his eyes closed to not see him. 

“You ever done penetration before?” Izuku asks.

Katsuki’s heart falls through the floor. “...Yeah.”

Izuku shifts. “Just because I know some omega men don’t like it as much and avoid it, and I don’t know what kind of experience you have but figured it would be good to ask before we mate and sorry if that was a weird thing to ask I just -”

“Izuku. S’fine. I…have before, but not.” Katsuki pauses, wishing for the hundredth time in the past twenty four hours that anything would spare him from this hell. Villain kidnapping, alien abduction. Anything. “Not with another person. I actually haven’t done…anything with another person.”

Izuku freezes. He sits up slowly, propping himself up so that his face is inches away from Katsuki’s. “Are you serious?”

“Why would I lie?”

“I didn’t know that was your first kiss.” Izuku says it softly, like it’s a secret.

“Yeah, well, I didn’t tell you because I didn’t want you to know.”

Katsuki feels like he’s going to throw up. He’s dangerously close to the truth, which is I didn’t kiss anyone because I never wanted to kiss anyone but you. And now my body is rioting if I don’t get to kiss you. Thanks for helping me out of this asinine predicament, lifelong best friend and hero partner of ten years.

“I care about you a lot, Kacchan. I need you to know that.”

Tears burn in Katsuki’s throat. “Course I know. It’s why you agreed to this shit in the first place.” His other words go unsaid. 

I care about you more than anything in this world.

I tried to live without you and I couldn’t.

Izuku presses a soft kiss to Katsuki’s forehead, just to add insult to injury. “Gonna go get us some water.”

Izuku brings the water and a few snacks, and in the time it takes for them to eat and readjust the nest, Katsuki once again feels like he’s going to burn alive from the inside. Exhaustion battles with arousal as they cuddle, their bodies slotted together. He tries to stop it, but before he knows it his mind is drifting away, his body pulled into sleep.

~~~

Katsuki wakes up in excruciating pain. He burns like a fire has been lit within his core. Instead of drifting awake peacefully, he’s shot to full alertness immediately. “Izuku,” he manages in strained syllables.

“Mm?” Izuku rolls in his sleep, clearly not being set alight from the inside. Alpha bastard. He’ll never have to deal with this shit.

“It hurts.” He hates the whine in his own voice, but it’s uncontrollable at this point. Maybe they should have just fucking gotten the mating over with. Fuck taking their time, this sucks.

Izuku finally stirs into a somewhat sitting position. As soon as his eyes land on Katsuki, he’s wide awake. “Oh my god, Kacchan. It smells so strong, what happened?”

Katsuki whines again, a keening sound down in his throat that’s more animal than human. “I need you. It hurts. It hurts.”

“Oh, baby, I know it hurts. Just hang in there. Heat must be in full swing by now.” Izuku’s hands are blessedly cool against Katsuki’s feverish skin. He holds his palms to Katsuki’s cheeks and forehead.

“Y’think?”

Izuku chuckles softly. “Let me get you an ice pack, okay? I’ll be right back.”

Katsuki feels his fangs drop and before he even knows what he’s doing, he hisses. Izuku stares at him in stunned silence. “Don’t leave. You can’t leave. I’ll go with you.”

Izuku looks like he might argue but takes a second glance at Katsuki’s fangs and nods. They shuffle into the kitchen together, Izuku supporting Katsuki at his waist. He picks Katsuki up and deposits him on the counter as he grabs a cooling towel that he’d (very smartly) put in the freezer earlier. He drapes it along Katsuki’s shoulders, and the cold seeps into Katsuki’s skin from the fabric, providing much needed relief. Izuku tries to help him down, but Katsuki hooks both his legs around Izuku’s waist.

He pulls Izuku flush against him and brings Izuku’s mouth to his. Izuku makes a surprised noise, but Katsuki just pushes harder. He thought he was feeling the effects of his heat earlier; it’s nothing compared to how he feels now. If he doesn’t have Izuku right this second, the world is going to come to an end. He will suffocate. He’ll die a second, much more embarrassing death.

He cups a hand around Izuku’s neck, tilting his head back for better access to drink in the kiss. His other hand grips wildly at Izuku’s waist. Earlier, the focus had entirely been on himself. Izuku hadn’t even taken his shirt off. Partly, that was because Katsuki was too self conscious to take any more than he was given. Now, no such mental reservations are in place, and he needs to touch every sliver of his alpha’s skin immediately. He runs his hand under Izuku’s shirt, feeling the dense, corded muscles under his palms. Good, strong alpha. 

Their hips are flush, and at the right angle he can feel the barest brush of Izuku’s hard cock against his own soaked boxers. Katsuki tears Izuku’s shirt off his head, and even that two second separation is too much. He licks a broad stripe up Izuku’s neck, suckling on his gland, savoring the minty aroma of old growth pine forests. It burns him from the inside, and there’s something so gratifying about knowing what Izuku tastes like at the basest level.

His mind runs wild with all the possibilities of what he could do. Selfishly, Katsuki never wants this to end. He wants to stay in this moment forever, with the promise of a lifetime of Izuku laid out before him. And maybe it’s not exactly how he wanted or expected it to happen, but it’s real, and Izuku is one hundred percent in. Katsuki won’t squander that.

Katsuki sucks a hard mark below Izuku’s ear and he actually moans. It’s the most delicious sound Katsuki’s ever heard and he needs more of it immediately, to hear how he can make his alpha feel good.

“Ah, Kacchan,” Izuku tightens his fingers in Katsuki’s hair. “Let’s go back to bed.”

Katsuki shakes his head. “Don’t fuckin’ care. I’ll have you here. Nothing wrong with the kitchen.”

Izuku actually laughs, the bastard. He clearly doesn’t understand how serious this is. Katsuki won’t make it to the bedroom. This is happening right now-

“HEY!” The kitchen careens around him as Izuku throws Katsuki over his shoulder.

Izuku just laughs and laughs, his grip staying strong even as Katsuki writhes and hits his back. Izuku drops him back into the nest and Katsuki actually bounces. Izuku has no fucking right to be that strong, he thinks.

And then Izuku is crawling on top of him, his full weight pinning Katsuki down into the mattress. Their tongues dance together in a rhythm they’ve managed to discover in just a few short hours. Perfect, Katsuki thinks. Perfect for me.

The next few minutes are a blur of skin and lips and sweat as the heat takes its mental toll. Izuku’s bare chest against his own is bliss, and the friction of Izuku thrusting their clothed crotches together is torture. Katsuki strips his own boxers and gets to work on Izuku’s sweats, because he’s far beyond the point of any nerves.

Izuku doesn’t hesitate to sink two fingers into Katsuki, and there’s no resistance since he’s still loose from earlier. Katsuki arches into it but whines when Izuku draws his fingers away. He almost snaps at him, but Izuku peels off his own boxers and coats his hard cock in Katsuki’s slick. There’s a thin sheen of sweat along Izuku’s chest and abs, his brow is furrowed, and he bites his bottom lip as he strokes himself. It’s the hottest thing Katsuki has ever seen.

Izuku looks at Katsuki from where he’s cradled between his legs. He runs a (not slick covered) hand up and down Katsuki’s thigh. His other hand still grips his dick. “You ready?”

Katsuki swallows. “C’mere,” he says, pulling Izuku down by his neck. The kiss is tender and sweet, full of the understanding that the both of them are standing on a precipice that they can’t back down from. All that’s left to do is jump.

Katsuki looks into the green eyes of his childhood best friend. He’s already died on the battlefield for this man. There’s nothing he wouldn’t do, no line he wouldn’t cross with Izuku by his side. “Ready.”

Izuku hikes Katsuki’s legs over his waist and then pushes in. It’s such a sweet relief to finally feel Izuku inside of him. There’s resistance at first, a burn as Izuku pushes in the tip because Izuku is fucking thick, jesus christ, but Katsuki bites his lip through it and then Izuku is sinking in to the hilt. The slide is so easy Katsuki almost laughs. Izuku fits so perfectly, like his body has been waiting for it specifically this whole time. It stretches him in the best way, presses against his walls with just the right amount of pressure.

“Doing okay?” Izuku asks.

Katsuki flashes a rare grin. “I’m fucking great.”

“Can’t believe I’m inside you, you feel so fucking good. So tight.” Izuku looks like he means it — his eyes are wide, his mouth open, and he’s fully focused on Katsuki. The look is almost reverent.

Izuku knows this is the first cock he’d ever taken, and it will probably be the only one now that they’re going to be mated. Katsuki relishes in the knowledge that Izuku is the only one he’ll ever have in this way, and that Izuku gets to experience being the one to fuck him for the first time.

Izuku’s first thrust has both of them moaning into each other’s mouths. It’s even more overwhelming than before to know that when he clenches around Izuku’s cock, Izuku thrusts into him harder, which makes Katsuki moan and clench again. It’s neverending. Izuku finds a rhythm, so deep and slow that Katsuki aches with it. Izuku buries his face in Katsuki’s shoulder and grips his thighs, his ass, his back. Katsuki loses himself in the waves of pleasure and just lets Izuku take the lead.

His heat addled mind is fuzzy now in a good way, coming in and out of focus. Izuku sucks on his ear again, traces a line of kisses all down his collarbone, sucks a bite onto the meat of his chest. When he brushes his tongue across a nipple, Katsuki actually jumps, his legs kicking out in surprise. Izuku moans into his chest. “Fuck. Fuck, you feel so good, Kacchan. You’ve gotta be careful, I need to last.”

Katsuki must have clenched around his cock. He almost does it again on purpose just to see Izuku’s reaction, strangely entranced by this newfound power, but he doesn’t have to when Izuku closes his teeth around the nipple. A loud, broken moan stutters from Katsuki as Izuku soothes the bite with a swirl of his tongue. Somehow, he still manages to keep moving through all of it, thrusting into a spot that makes Katsuki’s eyes roll back in his head and his toes curl.

He tries to form words, to say, I think I’m close, but all that comes out is another garbled moan. Izuku seems to get the message. “You almost there?”

Katsuki nods. Izuku kisses him, licking deep into his mouth. Katsuki feels so thoroughly claimed with Izuku’s tongue brushing against his own. He doesn’t need to ask Izuku if he’s close - he can feel the swell of a knot forming at the base of Izuku’s cock with each thrust. It pushes against his entrance, and Katsuki spares a wild thought that he’s going to have to fit that inside of him in a few short seconds. 

Katsuki’s tongue brushes along Izuku’s teeth to find that his fangs have dropped. They’re larger than his own, and the tang of venom coats Katsuki’s tongue.

This is it. Katsuki bares his neck. “C’mon, Izuku. Do it.”

Izuku’s eyes grow wide. His mouth can’t close around his fangs, so Katsuki can see the sheen of venom on his teeth. He hesitates.

Katsuki’s stomach plummets through the floor. Please don’t back down now. He bares his neck a little more, the skin the perfect target, laid out for Izuku’s taking. Please don’t make me beg.

Izuku nods, pulling Katsuki up into another filthy kiss. “Yes, Kacchan. I’ll do it. I’ll take care of you. My beautiful omega. You’re mine.”

Katsuki fights tears as Izuku breaks away and noses along his jawline. He threads his fingers through Izuku’s curls, holding on tight to something that can keep him grounded.

Izuku thrusts, one, two, three times, and then he’s pushing his knot into Katsuki. He cries out as it breaches him, a split second of white hot pain before warmth floods inside him. 

Izuku sinks his teeth into Katsuki’s neck.

It’s another flash of pain at first, accompanied by the sound of tearing muscle and crunching tendon. The sensation of the venom shooting through his veins is cool and soothing, the perfect antithesis to the ranging inferno of his heat. Blood trickles down his chest in thin streams.

Katsuki comes, his entire body tightening, sucking in Izuku’s cock so deep he can feel it from the outside. He reaches up just enough to sink his own smaller fangs into Izuku’s scent gland. He feels the skin rip underneath his teeth, and then his mouth is flooded with Izuku, Izuku, Izuku. 

The metallic taste of his blood mingles with the icy burn of pine and snow. Katsuki drinks it in, letting the liquid completely coat his tongue before swallowing. In this moment, consuming Izuku’s blood as Izuku drinks his, Katsuki feels as close as he can get to divine. They were always meant to be this close. They’ve shared a lifetime together - dreams, futures, even Izuku’s quirk. How had Katsuki survived this long without having Izuku in this way? Their souls were created to be intertwined. Their bodies were created to be embedded in each other.

Katsuki is finally, finally complete.

~~~

Katsuki wakes up in his bathtub. He blinks blearily through the steam from the warm water. Izuku sits next to the tub on a stool, a towel around his waist and his hair dripping onto his shoulders. The mirror is foggy and the singular light over the tub casts the bathroom in a warm glow.

“Hey, Kacchan.”

Izuku says the words with a soft smile. Katsuki pushes through his muffled mind, trying to make sense of where he is and what he last remembers - and then he sees it. A circle of teeth marks, right on Izuku’s scent gland. The angry wound stretches as Izuku swallows. Katsuki’s hand flies to his own neck to find a mound of gauze.

“I bandaged yours up since my fangs went pretty deep. It took a while for the bleeding to stop.”

Mate. The word rings through his head as he looks at Izuku. This is my mate.

“Thanks,” Katsuki mumbles, his fingers still pressed to his hammering pulse. “How long was I out?”

“A few hours. You feel asleep almost immediately. I stayed with you for a while, got you cleaned up, then went to go shower. When I was done you were still asleep, but I figured you’d appreciate waking up clean.”

Izuku’s right. Katsuki detests being unclean. It always grates him when he’s on multi-day missions in the field, but he toughs through it when necessary. He’s taken multiple showers a day for as long as he can remember just to keep up with his sweat build up. Cum, spit, and god knows what else has no place being on his skin for multiple hours. A hollow pang echoes through him with the realization that Izuku understands this all about him without Katsuki ever having explicitly told him.

The word comes to him again. Mate. And then - Alpha. Protector. Love. Pack. All the things that Izuku now symbolizes due to the bite in his neck. 

Izuku leaves Katsuki to finish washing, and when Katsuki re-emerges into his bedroom, the place isn’t as much of a wreck as he was expecting. Izuku removed all the soiled laundry from his nest and replaced it with fresh pieces. They’re folded neatly at the edge of the bed, waiting for Katsuki to place them exactly where he wishes within the nest. Izuku hands him a bottle of water. “You need to hydrate. You have a few more hours until the next wave kicks in.”

Katsuki’s mouth goes dry. “Shouldn’t be as bad. Now that we’ve mated.” He waves a hand at his neck.

Izuku’s eyes search his. “How are you feeling?”

“Alright. Tired, but good. I’m not in any pain.” He’s also halfway to completely losing his mind about this whole thing, but Izuku doesn’t need to know that. In fact, Izuku has slipped into the role of doting alpha staggeringly well. He hasn’t given any indication of his own feelings or concerns - he’s been one hundred percent focused on Katsuki since setting foot in his apartment. Hell, since seeing him that first time at the hospital. “What about you?”

Izuku shrugs. “If you’re okay, I’m okay, Kacchan. I’m glad you’re not in pain anymore.”

Katsuki frowns. He wants to press Izuku for more information, to uncover how he truly feels, but now is not the time, not when the next wave of arousal is only hours away.

“Do you want a change of scenery? I can set us up on the couch and we can play some games together. You should probably eat again, too.”

“Okay, nerd. Let’s do that.”

Izuku leaves him on the couch and then bustles around Katsuki’s apartment like he owns the place. He reheats soup for them, does a load of dishes, brings Katsuki a few pillows and blankets to provide the comfort of a nest even on the couch. 

They play a few rounds of Overwatch, and Izuku plays with an All Might skin like he always does. Katsuki teases him about it, but Izuku is such an expert he doesn’t have much ground to stand on. Katsuki hasn’t played many videogames, so they lose as often as they win, but Izuku doesn’t mind. Katsuki lets himself let go of his competitive nature, instead allowing himself to enjoy a rare day off from work, just hanging out with his best friend.

Eventually, that all too familiar itching frustration returns. Katsuki looks over at Izuku where he’s draped on the opposite end of the couch, knowing he’s the solution to all his problems. Izuku is laid back, his knees spread wide and his head lolled back on the couch cushion. From this angle, he has to look down through his lashes, and it’s so nonchalant and effortlessly sexy. Katsuki’s mating mark throbs.

Izuku’s eyes flash to his, and Katsuki goes hot all over. Could Izuku tell what he was thinking?

Not that it matters, Katsuki chastises himself. They’re mated, and Katsuki is still in the middle of a heat. They’re quite literally destined to have sex again in the next few hours, so there’s no need to be awkward. Regardless, the prospect of being the one to ask for physical attention from Izuku makes Katsuki want to rip his own hair out. He just so desperately wants control over anything, he doesn’t much care if it harms himself in the process.

Izuku pats the cushion next to him. “Do you wanna come here?”

Katsuki can’t deny affection when it’s so readily offered. He scooches over, his side just barely pressed against Izuku’s.

“Kacchan,” Izuku whines. “I meant come here.”

He grips Katsuki’s waist and tugs him square in his lap. Katsuki’s heart jams up in his throat as Izuku nuzzles his neck, scenting him thoroughly. It’s unlike anything Katsuki’s experienced before. Being scented on your neck is already very intimate, but Izuku leaves so much of his scent that Katsuki isn’t sure there’s any of his own left to put up a fight. Katsuki has only ever let his parents scent him, and on rare occasions, Kirishima and the rest of his friends, in a strictly platonic fashion. As in, barely. He’s never even needed their scents to comfort him through a heat. What Izuku is doing is intense and possessive, and it leaves Katsuki squirming in his lap.

Izuku relents, thank God, and wraps his arms around Katsuki so that he can still hold his controller. They just move on from that, like it didn’t happen. Like it doesn’t matter. Katsuki swallows hard. Is this how it’s going to be from now on?

They only make it through two more rounds before heat is once again licking through Katsuki’s insides. He tries to resist it, but Izuku is right there, and he finds himself moving his hips in the smallest of circles, hoping to feel the thick outline of Izuku’s cock against his ass. Izuku, the bastard, catches on before Katsuki can convince himself to stop. It turns into intense making out and Izuku’s hand between Katsuki’s thighs, fingers dipping in and out of his cunt until Katsuki’s dripping slick all over the couch.

He mourns the fate of the real leather, already dreading whether it’ll need to be professionally cleaned or entirely reupholstered. But then Izuku frees his cock from his sweats and slips it right inside Katsuki, and who fucking cares really? He’ll just buy an entirely new couch. He’d do anything for this feeling - Izuku thrusting deep inside him while he groans in his ear, each murmur of his voice sending a pulse of pleasure from his mating bite all through his body. 

“Alpha,” he whispers, equally a declaration of devotion and a plea. Izuku obliges, closing his palm around Katsuki’s cock until he’s spasming with an orgasm that has Izuku spilling deep inside of him. 

The next two days are a blur of the same routine - sex, shower, eat, sleep, more sex, repeat. Katsuki didn’t even think he liked sex this much, but his hormones are more valiant than he could have possibly imagined. Even after Izuku has bitten every inch of his skin and painted his insides with his cum, Katsuki still finds himself desperate for more only hours later. It’s never ending.

Except, eventually, it does end. The heat recedes, but the desire stays. The frantic need for it dissipates at least. Izuku doesn’t change though; he’s still as doting as ever. Katsuki thought it would fade with his heat, but Izuku still brings him meals and refreshes the nest and cleans him after every round of sex.

After what will hopefully be their last round for at least a day or two now that Katsuki’s heat has faded, Izuku cleans them up and repositions them in Katsuki’s nest with his laptop propped on his knees. Katsuki’s fading in and out, especially with Izuku’s fingers tracing feather light circles on his bare back. But Katsuki catches the glimpse of Izuku’s online shopping from the corner of his eye and nearly has a heart attack.

“Are you looking at collars?”

“Wah-cchan! I didn’t know you were awake.” Izuku’s face is red as a strawberry. His hand is halfway to the screen, like he can somehow cover up the evidence. “I was just - um -“

“Looking at collars? For me?”

“Maybe?”

“What makes you think I’d wear a collar?”

Izuku’s face is still red, but he pushes through, his voice a shaky mess. “Well, I was just thinking about it and - well Kacchan, your mating mark is pretty obvious. I mean, mine is small so I could cover it up with scent patches or makeup but yours is. Um.”

Izuku doesn’t need to finish the sentence. Katsuki’s fingers drift up to his mark subconsciously. It is a big mating mark - Izuku’s fangs are large and they sank in deep. It completely dominates Katsuki’s scent gland. It leaves no doubt that he’s a mated omega, so unless he wants everyone in a hundred meter radius to know he’s mated, he’ll have to cover it.

“Why can’t I just use scent patches? I may have to use a couple but it should be fine.”

“It’s really dark though. I think it might show through.”

Fuck. Katsuki really hadn’t thought this through. He hadn’t thought much further beyond survive mating with your best friend slash love of your life. But he didn’t particularly want to break it to everyone that he and Izuku had apparently started dating and mated within a two week span of time.

They aren’t even dating are they? Fuck. Katsuki is definitely keeping this to himself for as long as possible.

“Fine. Order the damn collar.”

Izuku lights up, and the scent of pleased alpha coats the room. “Really? Which one do you want, Kacchan? I really like this burgundy one, but I think the chain accents are a little much. What style do you like?”

Izuku rambles on and on about different collars he likes and dislikes, intermittently asking Katsuki’s opinion. It’s nice to be doing something so mundane for a couple together. Katsuki can almost pretend it’s real.

They purchase a plain black leather collar for daily wear. It’s thick and sturdy, and metal accents glint against the leather. When Izuku shows it to Katsuki, he’s almost angry that Izuku found something so perfect, something that he might have picked out for himself.For more formal wear, they choose a dark green collar that looks almost black until it hits the light. It reminds Katsuki of Izuku’s hair, and a thrill shoots up his spine at the idea of wearing something so clearly Deku around his throat. There will be no debate about who he belongs to.