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Dating Izuku, despite them both being alphas and having a history of a long, bitter rivalry going back to their childhood, has been a lot easier than Katsuki had anticipated.

For one, Izuku was somewhat of a submissive alpha. Katsuki definitely leaned into the aggression and dominating stereotype, and his partner didn’t seem to mind it all that much. The two of them enjoyed the occasional fight for dominance ending in sex, and wore their “battle scars” with pride. But Izuku didn’t mind having civil conversations about things when they argued, and even when his own less-than-pleasant alpha instincts reared their ugly head, Izuku had excellent control. Katsuki had even learned a thing or two from his boyfriend about controlling his instincts, though he would never admit that out loud.

They’d officially made it together for a couple months now, so Katsuki would say he and Izuku were doing very well for themselves as an alpha/alpha couple. Most alpha/alpha couples were just for a quick fling, or to explore some kind of kink, and they didn’t last much longer than a week or two at most. Izuku’s insistence on using reason over instincts had done most of the work keeping them together when it came to their shared secondary sex, coupled with Katsuki learning to atone for the actions that would upset Izuku.

The only thing that truly worried Katsuki, that had been on his mind recently, was something that Izuku had asked him about a couple weeks ago.

“Hey, Kacchan?” he asked, while they were lying in their den to sleep.

“What?” Katsuki grumbled, blinking himself back awake. He was already half asleep; what could the nerd possibly want with him?

“Sorry to wake you.” Izuku started stroking his fingers in Katsuki’s hair in a successful attempt to calm him. Damn Deku for knowing that was a weakness of his. “I just wanted to ask if you might want to start rut-sharing soon? It’s been a little while, and I’m kind of tired of being on suppressants when I have someone who could share that with me.”

Katsuki sat up and turned on the lamp on the nightstand. Turning his body back to his boyfriend, he squinted, furrowed his eyebrows, and looked him in the eyes. “Are you sure you want to do that?”

Izuku followed Katsuki’s motion, letting the covers layer on his lap. “I mean… I think so? I’m really serious about you, Kacchan. I know we’ve only been dating a couple months, but we’ve known each other for years… so I feel like I’m ready to take the next step.”

Katsuki had fiddled with his fingers, nervous at the idea, but he had been wanting to take another step with Izuku soon. “Can… Can I think about it?”

“Sure, Kacchan.” Izuku kissed him on the cheek. “I’ll stay on my suppressants until you decide.”

“Th… Thanks.” Katsuki leaned over to turn the lamp off and then crawled back under the covers to snuggle into Izuku’s chest. He gave the closest pec to his mouth a kiss. “Love you, nerd.”

“Heh, love you too, Kacchan.”

Katsuki banged his head on his desk at the office. He was a pro hero, dammit! Not only that, but he and his boyfriend were tied at being the number one heroes in Japan. What was he so fucking afraid of? He and Izuku had both handled all kinds of villains and monsters in their careers, even sensitive cases where the enemy couldn’t be killed or injured at all. They could absolutely handle each other’s ruts for All Might’s sake.

“Mr. DynaMight? Are you okay in there?” his secretary called through his office door. “That didn’t sound like the usual boom sound.”

“I’m fine, Ijichi. Nothing that concerns you.”

“Okay, Mr. DynaMight.”

Pulling his head off the desk, Katsuki whipped out his cell phone and sent a text to Izuku.

Kacchan: I’m ready to spend your rut with you.

Deku: Really?! YAY

Kacchan: This isn’t some playdate, don’t sound like a child

Deku: Sorry Kacchan, I’m just really happy!

Katsuki smirked as he looked at his phone. Yeah, he guessed he was happy and excited too. Besides… even with all the worries one might have for an alpha/alpha rut share, it was Deku. What’s the worst he would do? Cry about how much he loves Katsuki the whole time?

Dialing the number for their physician, Katsuki decided that setting up an appointment with him would be for the best regarding their safety. He wasn’t exactly looking forward to having his asshole sewn back together after taking Deku’s monster knot for a week straight. The blonde wasn’t oblivious; he knew how big Deku’s knot was normally, and he didn’t want to be unprepared for the even more inflated rut knot. Their doctor had an opening after Katsuki got off work, lucky for him, and he got up from his desk to change out of his hero costume and shower.

Izuku was out on patrol until the evening, so Katsuki didn’t bother waiting for him when he left the agency. He made his way to the train station, taking it to the other side of the city where his doctor was, and walked into the front office, going back to the examination room when he was called.

When he heard the locking mechanism on the door unlatch, Katsuki looked up at Dr. Iida Tensei as he wheeled into the examination room.

“So, Bakugou-san, I hear you’re wanting to rut-share with your partner?” he asked, spinning around in the corner to look at the current pro hero. Katsuki would always be grateful for Tensei as their doctor, since he was straight and to the point, but also because he had gone back to school to be a doctor for pro heroes specifically.

Katsuki nodded, opening his mouth when the doctor held up the popsicle stick and flashlight to check for strep. “We think it’s time for us to take that step. I’m not worried about anything in particular except that we’re both alphas, and Deku would have a freak-out if I didn’t prepare for this ‘the right way.’”

“Ah, I see. The ever careful Midoriya Izuku. And yet,” Dr. Tensei marked something down on his clipboard, “sometimes the least careful.”

The blonde snorted a laugh, remembering how his partner used to throw himself into the most dangerous situations just so he could say he gave it his all. Yeah, if you count “risking death every time” as something you give in a hero’s situation.

“Alright, let me run just a couple more tests. You seem to be perfectly healthy as always, Bakugou-san, but I just want to be sure. In the meantime, I’ll tell you that you need to keep track of Midoriya-san’s suppressant schedule: when he stops them, how long it’s been since, and the signs of his oncoming rut. You’re gonna need to keep a very sharp eye out for the signs, because for an alpha prime that’s been on suppressants for that long—”

“Wait, wait,” Katsuki spat, dead serious look in his eyes. “Say that again.”

“Which part?” Tensei asked.

“Deku is many things… but he’s not a prime.”

Tensei glanced at the nurse standing in the doorway, as if to say “are you kidding me?”

Katsuki scoffed, huffing a humorless laugh. “He’s not a prime. I mean… I never asked him, but he also never told me. He would’ve told me. I know he would’ve told me something like that.”

Taking a deep breath, Tensei put his clipboard down on the counter on the opposite side of the room. “Your partner is an alpha prime. His suppressants are extra strength, prescription strength, in fact. Perhaps his quirk developed later in life, but his genetics state that he’s been predisposed to present as alpha prime since birth.”

Slumping in the hospital bed, Katsuki thumped his head against the wall behind it, overwhelmed at the new knowledge. How come Deku never told him…?

“You know what,” Katsuki blurted after a moment of silence while he was processing everything, “The nerd probably didn’t think it was important. Fucking… bastard. I’ll get him for this when he gets home. Just… keep going, doc.”

Tensei nodded, realizing this was going to be the first of Katsuki’s meltdowns. He’d witnessed many so far, and he and the rest of his staff know that this was on the mild end of his spectrum.

“As I was saying before,” the doctor resumed, “Your partner is an alpha prime who is coming off of years of suppressants. His rut is going to come hard and fast, pun intended. You need to make sure you’ve got a ridiculous amount of food stocked, meat and carbohydrate-heavy food specifically, and I mean that. Go to one of those bulk stores outside of the city; they’ve got everything you could need for much cheaper than you can find here.”

“How much food are we talking?” Katsuki asked, scrunching up his eyebrows in concern, and perhaps a little fear.

“Like you’re responsible for all the food at a pro hero cookout.”

“Fuck.”

“Yeah. Cook things that you can eat cold, or heat up really easily, if you must cook them at all. Alphas enjoy when their partner shows how they can contribute to taking care of the household, especially since you’re both alphas, and also, Midoriya-san will be less reluctant to eat if you say that you cooked it for him.” Tensei pursed his lips, not meeting Katsuki’s eyes for a moment as he thought of how to phrase the next part. “More than likely, you’re going to have to wear a plug from the moment you notice the signs of rut starting, in between penetrations, and a little while after Midoriya-san’s rut is over. Get used to the idea of Midoriya-san thinking of you as an omega in need of breeding, and treating you in the same way while he’s in rut. He’s got a medical history of not remembering what happens during ruts, so that’s a possibility for you to look out for.”

Katsuki blinked.

“He has a medical history of what now?”

“Midoriya-san has a history of not remembering the things that have happened during his ruts. Has he not discussed this with you?”

Katsuki sat back against the wall, thunking the back of his skull against the drywall. “You’re serious?”

“Afraid so.”

There was an awkward pause as the weight of that fact sunk in. Eventually, Katsuki pulled his head up from the wall and sighed, closing his eyes while he processed everything.

“I guess we’ll cross that bridge when we get to it. I’m a hero after all, right? I can take anything that nerd has got to throw at me.”

Tensei sighed, covering his face with his hands as he leaned forward on his elbows. “If you say so, Bakugou-san. Just promise me that you’ll do your best to follow the instructions that I’ve given you today? I know you think you can handle this but I just want to be safe. Two alphas rut-sharing together has ended in many messy investigations and injuries, and I don’t want anything biological to ruin the relationship between the two of you.”

Katsuki took a deep breath, nodding solemnly as he fixed his posture. He pursed his lips and sat up from the examination bed, making a move to stand up. “I’ll make sure nothing happens. We’ve been through pretty much everything so far… and only gotten stronger each time. I don’t see what would be different now.”

“That’s… a good thought process to have about this kind of thing, actually. Good luck, Bakugou-san.”

“Thanks, I guess. See you when it’s all over,” Katsuki grumbled as he stood up and made to leave the room.

“I’ll see you then.”

Whatever Katsuki had been expecting out of rut-sharing with Izuku, this had certainly not been it.

He could barely move. Every motion he made, no matter how small, caused some kind of soreness in his body, especially in his core and his hips. He didn’t want to think about how all the claiming bites and scratches looked on his body, how he was bruised in the shape of Izuku’s hands all over, and how in the hell he was going to explain this to media coverage once the two of them returned to hero work.

Izuku, just as the doctor had told Katsuki, had not remembered anything when they had come out of their haze. Despite that, though, he saw the damage he’d done to Katsuki, and was nothing if not an absolute angel with the aftercare. Katsuki felt like he was being coddled a little bit, like a whiny omega, but being taken care of like that wasn’t so bad, he decided. Yeah, the hot water in the bath stung the first couple of times that Izuku drew him one and carried him into the tub, but Katsuki never had to lift a finger the week after Izuku’s rut.

He kinda… saw the appeal of being a good house omega, if this is what a proper providing alpha was intended to be like. He certainly wouldn’t ever call himself that, but he could see the appeal.

“Kacchan?” Izuku called from the door of their bathroom.

“Yeah?”

“I made a fruit tray for you, if you want it.”

“God, yes.”

“Heh, okay,” his alpha huffed a laugh, dragging the vanity stool next to their porcelain bathtub. “Can I feed you?”

Snorting in reply, Katsuki laid his head back against the edge of the tub. “What about the current state of my body—entirely caused by you, you fucking brute—says that I am capable of feeding myself?”

Izuku’s face lit up in a smile, and Katsuki relished in the fact that now his teasing made the alpha laugh rather than cry. “I guess nothing.” He grabbed the fork he’d brought with him, stabbing a cube of watermelon before holding it up to Katsuki’s mouth.

“That’s what I thought, nerd,” he breathed, eating the fruit and feeling a little ridiculous, but well taken care of.

Katsuki didn’t feel so good.

He and Izuku had been on opposite work schedules. Complete opposite. Night shift and day shift. The only time the two alphas could have to themselves were quick breakfasts to start their day and take-out dinner eaten in the living room that served the same function. So, perhaps, Katsuki thought at first, that maybe it was just him missing his partner. The last time he’d felt this lonely was when Izuku was studying abroad in America.

But it wasn’t just loneliness. Sure, he missed his alpha, but it was a little more fundamental than that. Something biologically had to be happening… because loneliness doesn’t cause severe abdominal cramps. Loneliness doesn’t cause pain that’s intense enough to make a person vomit, and loneliness certainly doesn’t cause stinging between his legs, as much as he wished he could chalk it up to their lack of sex.

So Katsuki called Dr. Tensei. And he was on time for his appointment the next day despite having to leave work early to go see him.

Dr. Tensei was thorough in his exam, though quiet as he went through the motions. Katsuki winced when he reached between his legs, gentle gloved fingers prodding where it stung, and the pro hero even let a whine or two escape his lips. As Dr. Tensei prodded him more, pain in the form of electricity crackled along his skin, stinging on the outside and turning into rolling lava that ached in the lower part of his belly as it moved inward.

“Ow, ow, fuck… Why’s that hurt? Shit.”

“Bakugou-san, please relax. The more you tense, the more pain you cause yourself. It’s tender as it is.”

“What’s tender?” Squeezing his eyes shut, Katsuki tried his best to uncoil the constriction in his body.

Dr. Tensei only sighed in response. “I will give you the details once I finish the examination.”

Katsuki huffed, letting his legs fall gently onto the table.

Tensei replaced the examination robe so that it covered Katsuki’s body, preserving his modesty.

“So… First of all, you’re fine. Your body is going through… changes,” he began.

“Changes? What kind of—”

Holding up his hand, Dr. Tensei interrupted Katsuki’s question. “I want to give you and Midoriya-san congratulations.”

Katsuki’s brows furrowed as a headache began forming behind his eyes. “For what?”

“Congratulations on a successful bitching.”

The world around Dr. Tensei became blurry as the pro hero’s brain tried to process what was happening. Katsuki inhaled sharply, blinking repeatedly as the information seeded itself and took hold.

“Are you alright, Bakugou-san?” Tensei asked, reaching to put his hand on the bed next to the pro hero.

“We… I didn’t know this had happened.”

The doctor sat back, eyes wide with concern. “So this was… not consensual?”

Katsuki made steady efforts to control his breathing to prevent his oncoming panic attack. Shutting his eyes, he leaned his head back until he was leaning on the wall behind him, counting with each inhale and exhale.

“What should I do?” he mumbled around his clenched teeth.

“I’m sorry, could you repeat that?”

“What. Should. I. Do. Now?” Katsuki’s words were biting as they left his lips.

Tensei reached behind him and pulled his clipboard off the counter. “Well, your body has already entered a stage from which it can’t be returned. Finishing the process somewhat painlessly involves you ingesting as much of your alpha’s semen as possible to move it along faster, but I understand if that becomes an impossible option. If you decide to let it finish without Midoriya-san, then I have a contact that I can refer you to that specializes in bitching and studding. For now, I have prescribed some hormone balancers and pain medications when you’re feeling the cramping particularly badly. The analgesics are intended to be taken only when you need them, and you should not attempt driving, handling potentially hazardous equipment, or hero work while you’re under their influence.”

Katsuki merely nodded, numb to his new reality for the moment. He sits up and hops off the examination bed gently. “Anything else?”

“Well,” the doctor began once more, disengaging the brakes on his wheelchair, “You should avoid using your new… equipment, until you enter your first heat. If you and Midoriya-san remain as you are and he helps with the rest of the process, then he should be your partner for that first heat. If things don’t work out, though, you should try to ride it out on your own.”

Katsuki grunted in affirmation, making his way to the examination door to open it. “Thanks, I guess.”

Tensei let the pro hero leave with his dignity, hoping this wouldn’t be the end of Japan’s number one and two wonder duo.

When Izuku arrived at home, he wasn’t expecting Katsuki to have drowned himself in liquor. His partner wasn’t much of a drinker, so to see him in the state of intoxication he was in was very unusual.

“Kacchan?”

The blonde snapped up at the sound of the nickname. “Don’t fucking call me that, Deku!”

Some deep part of Izuku immediately went into fight or flight at the tone of Katsuki’s voice. It carried something angry and violent toward him that he hadn’t experienced in a very long time.

“K-Katsuki, what’s going on?” he asked, pushing past his own anxiety to sit in the chair across from his partner.

“Fucking Deku, this is all your fault. Your fault, your fault!” Katsuki spat.

“What’s my fault? You have to tell me, or I can’t find a way to help.”

“Help?! Oh, you’ve helped enough,” the explosion hero slurred, holding his head as he sat up from lying down on the couch.

Izuku continued to aim his confused, questioning look at the blonde, silently begging him to elaborate while he got settled in their living room.

“You know what? You’ve been gone, we’ve been off schedule so much that I bet you haven’t even fuckin’ noticed.” Katsuki rolled his eyes as Izuku only continued to pin that stupid look at him. “I’ve had stomach cramps, I couldn’t walk for like a week, I don’t have the stamina for hero work that I used to… I have to sit down for like an hour after a normal shift with no overtime now, because of you. Ever since we rut shared…”

Izuku’s eyes widened. “You’ve been experiencing all of that?”

Katsuki pursed his lips, finally lowering his volume as his anger turned into grief. Those pretty carmine eyes turned glossy with unshed tears. “Yes. Yes I have, you fucking moron.”

Careful in his movements as to not cause Katsuki anymore of a physical breakdown, Izuku shifted from the chair to the couch next to his partner. “I’m sorry, Katsuki. I guess I got sucked into work again. I had no idea you were experiencing that. Have you gone to the doctor yet?”

The tears resting in Katsuki’s eyes made good on their threat to fall, spilling over the corners onto his high cheekbones as he steadied his breathing. “Yes. I did go.”

“Are you okay, Katsuki?” Izuku’s heart rattled in his ribcage as worry set in. Was his lover okay?

Katsuki shrugged, and then crawled into the other alpha’s lap, much to his surprise. He mumbled something into the crook of his neck.

“What was that?”

“‘M fine. Doc said that I’ve been bitched, is all.”

Izuku was ashamed to say that he only panicked about that statement for a brief moment before arousal set in.

Katsuki ripped his head away from Izuku’s neck, looking at him incredulously. “Are you fucking kidding me? That turned you on?”

“Sorry, I’m sorry Kacchan, I know this is serious.” Izuku squeezed his eyes shut as he tried to refocus, taking a deep breath and exhaling harshly. “Are you still in pain? I… what do we do?”

His partner wouldn’t meet his eyes. “I didn’t… I didn’t want to be bitched. But… Dr. Tensei said it’s irreversible now. I can’t even begin to think of the headlines once news of this gets out…”

Izuku ran his fingers through Katsuki’s hair, stroking his cheek and watching the insecurities settle on the blonde’s face. The former alpha’s voice was soft when he spoke again.

“I love you, Izuku… but I don’t know if we can recover from this. I’ll be different. I’ll be submissive to your commands, and have to take time off for heats because omega suppressants fuck up your system, and and and—”

“Katsuki. You’re panicking.”

Izuku’s voice was steady as he focused on helping his partner calm down. He knew that normally using his scent to influence Katsuki didn’t work, that it usually just made him angrier. This time, though, when his calming pheromones rolled off his scent glands in waves, Katsuki’s hyperventilating began to even out, and his glare softened as he breathed with his mouth open.

“If… if you need some space from me, then I understand. I didn’t think sharing my rut with you would cause this. I’m sorry that you’re going through these changes when you didn’t want them, but I hope you won’t want to give up on us completely.”

Katsuki tilted his head before snorting and tucking his face in the crook of Izuku’s neck. “Might as well. This is a stigma we’ve been fighting against since we got together. We just became a stereotype.”

“I don’t care about that, Katsuki. I just care about you. I want you to come out of this healthy, so if I can help, please let me help.”

The blonde shut his eyes and leaned on Izuku’s shoulder. “I’m tired. Can we figure this out tomorrow? I took the day off.” His cheeks were still pink from the alcohol consumption, and Izuku thought he was adorable.

“Yeah. I have the weekend off, and I’ve asked them not to call me unless it’s a code red emergency. I’m tired from my week, too.”

Izuku got up from the couch, lifting Katsuki with him, and carried them both to their bedroom to rest. They had a lot to consider in the morning.

Katsuki decided he could forgive Izuku. The alpha prime didn’t realize that bitching was possible just from rut sharing, and he apologized to Katsuki for not explaining his prime status when they got together. Izuku really did try his best to lessen the effects of things for Katsuki, and make sure he was comfortable.

It wasn’t very long before they were back to having sex again. Their schedules became more consistent, and Katsuki found himself with a higher libido than normal the more he got to see his alpha. He’d jump the alpha when he got home from work, kissing his neck and nuzzling his scent gland until his cheeks were pink and warm.

The nesting behavior came first. Katsuki scoured the whole house looking for blankets and Izuku’s clothes to add to the walls of his nest in their bed. He was very careful to pick out the best textures and lay them in just the right arrangement, and he found himself looking up at Izuku for approval, even though the thought made him want to puke.

“Perfect, Kacchan.”

And Katsuki would blush and invite him into the nest.

Izuku still had magic fingers, reaching all the spots inside Katsuki that made him gasp and moan and shake. It was really easy for Katsuki to cum, as time went on, and his cock kept getting smaller, his balls drawing up and reshaping into the outer lips that he knew would surround his pussy soon.

As weird as it was for Katsuki to adjust to, as soon as his heat started, he’d finally satiated the curiosity of wondering what the omegan orgasm was like. Middle school alphas everywhere had to be jealous in some way.

Katsuki asked Izuku if he ever missed bottoming. And Izuku was honest when he said he didn’t. Katsuki was more appalled with himself when he realized he didn’t really find topping all that interesting anymore either. Even though his alpha couldn’t fuck his new pussy just yet, Katsuki still craved the full feeling he got when his alpha bottomed out inside his ass.

The next thing to change was Katsuki’s scent. It was like a campfire and dark chocolate before, comforting and alluring all at once. Katsuki was settling in for another day off as Izuku got ready for work, and the alpha prime couldn't keep his nose out of Katsuki’s neck.

“‘Zuku, stop it,” Katsuki whined, trying to shy away from Izuku’s scenting when his glands felt raw.

“But Kacchan, you smell so good. You smell sweeter…” the alpha murmured, getting one last lick on Katsuki’s neck before heading for the door.

“I do? What do I smell like?”

“Like… There’s these treats we used to eat when we went camping in America. They called them s’mores… You’d roast marshmallows over the fire, and then put it in between a piece of a chocolate bar and graham crackers. You smell like those.”

Katsuki blinked. “Burnt marshmallows and chocolate?”

Izuku shrugged and nodded. “It was delicious.” The alpha gave Katsuki a kiss on his nose and then left for his work day.

It was shortly after Izuku left that Katsuk’s new omega brain decided he needed to scent everything in the house, right now immediately. And Izuku rewarded him that evening by fucking him hard.

Katsuki’s appetite shifted after that, too. He thought before that he ate enough to feed a small army, since his metabolism was fast and he was constantly moving and exercising, but his new appetite was enough to feed an entire legion. Despite continuing to exercise and keep up with his training regimen, Katsuki started to see areas of his body begin to soften, namely his hips, pecs, ass, and his face. Once he got accustomed to the changes, he couldn’t lie that he was actually… a quite attractive omega.

On days that Izuku was working, and Katsuki had a little time to himself, he’d stand in front of the mirror and admire all the new changes, dragging his hands over his cheeks and jaw, across the top of his pecs down to his waist.

“Shit. It looks so tiny...” he commented to himself as he rested his hands on either side and squeezed. Red inflamed his face as he blushed, thinking about how Izuku would react once he realized, the oblivious fucker. Katsuki dragged his hands across the curve of his hips, marveled to find there was no dip, just a smooth curvature for his alpha to adore and grab onto while he railed him.

Watching the changes in his own body started to become less alien and more natural, but the changes in his instincts were the ones that shocked him the most. It wasn’t that Katsuki didn’t like sucking Izuku’s dick before—he most certainly did—but he found that his body responded a lot easier to the alpha prime. Ingesting Izuku’s cum was something he knew they needed to do in order to move the bitching process along as painlessly as possible, so Katsuki figured he’d have to push past the alpha instincts that still remained. His esophagus still rejected it every time Izuku tried to cum down his throat, so they decided to try some things different until it became easier for Katsuki to suck his dick.

Izuku expressed that he felt a little silly ejaculating into the blender pitcher, making sure to get all his seed inside before his omega-to-be blended it into his protein shake. Katsuki, though, found that it did the trick. He started collecting it from Izuku and mixing it into his food, labeling the things that were meant for Katsuki’s bitching in the fridge so the alpha prime didn’t eat it by mistake. In combination with this, Katsuki would attempt to deep throat Izuku every day until finally, three weeks later, something felt different.

Katsuki sat on their bedroom floor on his knees, right in front of where Izuku was standing and leaning against the bed, both of them naked. The alpha prime stroked his cock a few times before placing the head on Katsuki’s bottom lip, waiting for him to open his mouth. Katsuki inhaled the scent of Izuku’s alpha musk, blinking a couple times before realizing that he was… about to drool. It was like all of a sudden, his mouth decided he needed to be producing saliva, and it made way too much.

Brushing the thought away, Katsuki opened his mouth and popped Izuku’s cockhead behind his pink lips, giving him the kitten licks and sucks on the head that he knew his alpha liked. He didn’t have the usual difficulty with sucking his dick as he usually did, so Katsuki thought that had to do with the fact that maybe he was just getting accustomed to doing it all the time. But, when Izuku started panting, thrusts becoming uneven and jerky, his gentle pushes of his cock down his hole were met with no resistance. Both of their eyes widened as Izuku bottomed out without any trouble, Katsuki’s nose in his pubes at his lower belly. Tears spilled from Katsuki’s eyes in pleasure as he felt Izuku’s seed go down his throat and settle heavy and warm in his belly, the flow seemingly not stopping any time soon.

Once Izuku was confident in pulling out without spilling anything, he and Katsuki looked at each other like a miracle had just occurred. The explosion hero licked the last drops from the roof of his mouth and swallowed, grinning maniacally when he realized what this meant for them.

“You better pray your stamina comes through for you, shitty Deku; we’re doing that again.”

“Kacchan—”

Katsuki craved Izuku’s cum afterward. He found himself falling to his knees every time the number one hero came home, jaw dropping to take his cock all the way to the hilt and swallow his seed.

The signs of his heat came on before they knew it, and Katsuki found it silly needing to ask for “rut leave,” since he wouldn’t be fully registered as omega until after his first heat. But they granted him the personal leave time regardless, and Izuku was more than happy to hear that things were starting. They paid a visit to Dr. Tensei in order to learn when the signal for “Katsuki’s ready, you can go now” would make itself known, and began preparing for heat.

Izuku stocked the entire kitchen with things that would be easy to make. He bought a mini fridge and left it upstairs to keep water and fruit in, clearly very happy to be indulging in alpha behaviors that he didn’t get to access before for fear of angering his alpha partner. Katsuki found it endearing, even though he never voiced it, just added more clothes and blankets to his nest in their bed. The walls of the nest came together relatively easily, despite Katsuki being extremely particular about how he wanted everything to be placed; Izuku was a godsend, running off to get every little thing that the new omega could possibly want or need.

It was right at daybreak when Katsuki felt the first wave. Waking up to wet boxer briefs, he groaned and rolled over onto his stomach, finding no relief when his skin was sticky with sweat. Once he kicked off the covers and tried to sit up too fast, his vision began to fog while his head started spinning, the haze of arousal flooding his senses at the same time as the cramping pains in his abdomen.

A very omegan whine escaped his throat and went past his lips, turning into soft gasps as he laid back down and curled into the fetal position. He reached his hand toward Izuku’s sleeping form next to him, inhaling sharply as another cramp spread in his lower belly.

“Izuku… I-Izuku…!”

The newly presented omega heard the sheets rustling next to them, and then felt the heat of his alpha’s body as he inched closer to him.

“Kacchan? You alright?” he yawned, taking a moment to register being conscious before figuring out what was happening to his partner.

“Izuku… hurts, please, it hurts…”

“Oh shit!”

Izuku was shoving the blankets off of them and shooting up into a sitting position, lifting Katsuki so that he sat in his lap. He started lazily kissing Katsuki’s neck, making the omega gasp and moan. Was he really that sensitive? Had so much really changed?

“Kacchan… god, you smell good.”

Katsuki whined.

“You’re gonna be the death of me, baby.” Izuku’s hands felt so big on Katsuki’s body, roaming in all the same places as before, but it all felt so new. The alpha’s hands felt huge as they wrapped around his little waist, fingertips coming very close to touching on his back, and even bigger when they came back to Katsuki’s front, squeezing his pecs that had grown into small breasts in a matter of a few weeks.

“I’ve loved you for so long, Kacchan… but it’s like finally our instincts understand it too.” Izuku held Katsuki as he laid him on his back in the nest, crawling over him to touch their foreheads together. “It’s like we’re new. I knew we were meant to be, but now it feels even more like that.”

Katsuki whined, leaning his face up towards Izuku.

“What is it, baby? You want a kiss?”

Katsuki nodded, swallowing the lump in his throat as his pride was overtaken by his instincts. “Kiss… kiss, alpha.”

Izuku’s pupils blew wide as he couldn’t resist his omega anymore, capturing Katsuki’s soft, plump lips with his own chapped pair. He swallowed all the sweet submissive sounds from his Kacchan, pinching his nipples softly and relishing in the small yelp that went straight into his mouth. Drifting his hands down Katsuki’s slightly soft tummy, he pulled down Katsuki’s boxer briefs and stared in awe at the slick that stuck in a string until he pulled it far away enough to snap.

There, before him, was Katsuki’s pussy. The lips surrounding it were puffy and soft, covered in clear, sticky slick and swollen in an attempt to entice the alpha to just put it in. Katsuki’s clit was hard and throbbing, sticking up a little past the lips and flushed red like the blush on his omega’s face.

Izuku needed his mouth on it. Now.

“Ah!” Katsuki gasped, throwing his head back onto the pillow underneath him as Izuku crawled between his legs and wrapped his lips around his clit, sucking with enough pressure for it to feel like everything all at once. “Izuku.. Alpha, alpha…”

The alpha in question groaned into Katsuki’s pussy, licking his tongue over the newly formed vaginal canal.

Katsuki screamed.

“A-Alpha! Oh…”

Izuku growled as he got more confident, pushing his tongue inside the hole gently and tasting all the sweet slick from the source. Katsuki’s gasps and moans only spurred him on further, and the alpha lost himself to his instincts as he drowned happily in the sweet scent of s’mores and caramel coming from his omega. Carefully, he reached up and pushed one of his fingers inside Katsuki, blinking his eyes closed in bliss when he got the most adorable little gasp in response.

“Shh, I’ve got you, omega.” Katsuki’s whole body convulsed as he arched off the bed, whining and trembling with the word from Izuku’s mouth. “You liked that? When I call you omega?”

Katsuki’s eyebrows scrunched together as he hid behind his hands, rolling his head to the side. Aw, he was embarrassed about cumming from penetration alone.

Clicking his tongue in disappointment, Izuku pushed another finger inside Katsuki, watching with rapt attention as his pussy opened up so much more easily than his ass. And with each careful movement of his fingers, Katsuki responded so cutely, spreading his legs further as Izuku stretched his walls open.

Four fingers in, just to be safe, Izuku finally began to make out words in between the cute needy whines that his omega was breathing.

“What’s that, Kacchan?”

“Alpha… please, it hurts, ‘m empty, please please please…”

“Okay, okay, omega. I’ve got you. Alpha will take care of you.”

Izuku couldn’t resist licking the slick off of his fingers as he rose up from between Katsuki’s thighs, replacing his head with the tip of his cock as he rolled it around in the slick.

Katsuki, poor thing, just whined some more, rolling his hips down and hoping Izuku would grant him what he wanted.

“Tell me if it hurts, okay, Kacchan?”

The omega only nodded, and with his consent, he pushed his cock inside the pussy he’s been dreaming about for months.

They both froze, gasping and groaning at the stretch and the tightness. Something in their brains clicked, locking the two of them together when they made eye contact. Izuku pushed Katsuki’s knees up on either side of his waist, and sealed their lips in a kiss, starting to move his hips gently.

Katsuki’s whimpers and whines were so cute, and Izuku couldn’t wait to hear them turn into yelps and screams of pleasure. An annoyed sound came from the omega, though, and Izuku pulled back to give him a questioning look.

“‘M not gonna break, nerd… More.”

Izuku growled as his alpha fangs dropped, leaning onto the back of Katsuki’s thighs to gain leverage as he slid his hips back and forth, thrusting in and out of the omega as he wailed. Tears lined the edge of Katsuki’s eyes while he gasped and hiccuped in pleasure, not even a hint of discomfort in his overwhelming scent. The alpha had tunnel vision for his omega as he lost control of his mouth to his instincts.

“Gonna… knot you, Kacchan… Get you pregnant. Give you my pups…”

“A-Alpha! Izuku, ‘zuku, alpha, please please…”

“You’ll be so pretty hanging off my knot, belly round with my cum… You’re gonna take it all, aren’t you?”

Katsuki nodded and begged, begged like he’s never begged in his life, because nothing sounded better to him than being pupped and filled with his alpha’s seed. He felt Izuku’s knot start expanding and sucking in and out of his cunt, and his pleas escalated, turning loud and desperate and everything Izuku needed to hear.

“Shit, babe, I’m cumming… fuck.”

Izuku doesn’t think his knot has ever expanded so fast in his life.

Once he locked inside Katsuki, his omega’s body spasmed without even a touch to his clit, walls pulsating around Izuku’s knot as it milked him for all he was worth. Izuku leaned down to scent Katsuki, kissing and licking his neck in an attempt to help him come down from his high.

“Alpha… alpha, please…”

“Please what, Kacchan?” the alpha asked, caressing his cheek.

“Please, mate, bite…”

Izuku’s eyes widened as he felt his instincts answer for him. Those alpha fangs got put to use as they buried themselves in Katsuki’s neck, all the alpha’s anxiety about his impulsive choice quelled when all he could feel through their new bond was overwhelming happiness. Izuku wasn’t sure if he knew that Katsuki had felt something like that before. His walls clenched around the alpha’s knot as he finally, finally, could use a bond to communicate everything he was feeling to Izuku.

No more constipated words. No more shitty communication skills. Just him, his alpha, and their empathy link that came with a mating bond.

Izuku’s eyes began to well up with tears as he started to understand the extent of the love his Katsuki felt for him.

And Katsuki’s familiar grimace formed on his face as he came to lucidity.

“Stupid nerd… don’t cry.”

Izuku scooped him up into his lap and kissed and licked his new bite mark, making sure it was sealed to scar over properly.

“I love you, Kacchan.”

“I…” Katsuki tried to swallow, despite his throat being so dry. “Love you too, nerd. But ‘m tired. Can we go back to sleep?”

Izuku smiled and nodded, wiping his tears away as he leaned over to the mini fridge and grabbed a bottle of water.

They were going to be okay. They always were.

The hero world, though? They’d have to wait a while to learn what the top two heroes were up to these days.