Chapter Text
That stupid fucking kid was following him around again.
They were neighbors. Katsuki had been sort-of babysitting Izuku ever since he was an infant. It was the only way to get out of the house as a nine-year-old when his mother wouldn’t stop nagging him to take responsibility and do his chores, or homework, or whatever else she bothered him to do. It was easy to lie and say he was going to help Auntie Inko with her new baby, and admittedly, he’d been cute at the time but that was when he couldn’t talk. As he grew older he grew dumber and started to annoy the shit out of Katsuki, what with his creepy All Might obsession and overly cheerful personality.
Auntie Inko was a cheerful woman, too, but the birth of her son had magnified the trait by a thousand. Every time Katsuki stopped by to say hello – not to babysit, he insisted – the kid would run to him and jump up in his arms, and of course he had to catch him otherwise Auntie would be upset. He could care less honestly, and on some occasions, when Auntie wasn’t looking or had just left, he’d let the kid slip from his grip and fall on his butt.
Katsuki never felt bad.
…Well, that’s what he told himself. Izuku’s tears were big and his sniffling made something in Katsuki’s chest get all tight and achy, and he knew Izuku was one for extreme waterworks; so Katsuki would quickly pick him back up and mumble an apology. He’d rub Izuku’s back and ask him if he was okay, let the useless little boy cling to him and tell him things in that baby garble that only parents could understand. He would nod along regardless as if he could understand Izuku’s mumbling – a quirk that never went away itself, as Kastuki learned once the boy could speak clearer Japanese.
Within seconds Izuku would return to his normal self, keeping his stubby arms wrapped around Katsuki’s neck. Cuddling was his favorite thing to do and the only way to get him down for naptime back in those days.
Katsuki stopped walking. The kid bumped into his sagging pants with a childish “Oof!” and fell backward on his butt, but he didn’t cry. He giggled like any child would over a harmless fall.
“Kacchan!” he said happily. “Can you come over and play with me today?”
“No, you useless fucking brat,” he growled beneath his breath.
“Ooh! You said a bad word!”
“Shut up, Deku!”
“Hey, I’m not useless!”
Izuku crossed his little arms. Katsuki turned around to find the most adorable little pout on his lips and was tempted to squish those cheeks together—scratch that, he decided to do it anyway, smirking at the surprised yelp that came from Izuku’s mouth.
“Look here, you little brat,” he began, “You know what U.A. is, don’t you?”
“Hee-wo Aca-mmy!” he said with those stupid little fish lips.
“That’s right, and I got accepted there. I’m training to become a hero and I can’t do that with you following me around like a damn puppy dog—shut up! I can say what I want!” Katsuki straightened his back and cleared his throat. “I’m gonna be late for class, nerd. Go back home. I’ll stop by today.”
“Yay, Kacchan’s coming over!”
“And don’t you dare tell Auntie about the bad words.”
Izuku smiled mischievously. “Only if you promise to come over! Don’t forget like last time.”
God fucking dammit, Katsuki thought, there he goes with that damned sad frown. Katsuki took a deep breath and calmly exhaled through his mouth. “Fine,” he said. “I promise.”
“Pinky promise!”
“Ugh! You useless brat, you’re gonna make me miss my train!”
Katsuki didn’t want to fulfill his promise, but he recalled the many times he ditched playdates with Izuku to hang out with his friends or play video games at home alone and cringed. The boy knew how to throw a tantrum and when Auntie Inko told his mother about it, she gave him a fucking earful, too. “He just adores you so much, Katsuki!” Auntie would gush, and when she said it, he started to feel bad. His mother would eventually make him go next door to apologize and make up the playdate with Izuku before she let him back in the house.
Begrudgingly, he knocked on the door. He was all beat up from battle training, but tried to clean up the scrapes and bruises on his face to prevent Auntie from worrying.
“Kacchan! Kacchan!”
Of course the child’s muffled voice could be heard along with his padding footsteps. Auntie opened the door with a smile, welcoming Katsuki in.
“Katsuki, do you mind putting Izuku to bed?” Auntie Inko asked. She yawned real big before continuing. “I’ve been doing overtime all week and I’m fairly exhausted myself. I can compensate you, of course!”
“No need, Auntie, I’ll put him to bed. Eight o’clock, right?”
“Oh, Katsuki, you’re so wonderful! Thank you. Goodnight, you two! Izuku, behave for Katsuki.”
Izuku hugged Katsuki’s leg tighter with his arms, not listening to a word she said. Katsuki rolled his eyes, ruffling fluffy green curls as he said, “C’mon, nerd, let’s go watch TV or something.”
They were halfway through some climactic episode of one of Izuku’s favorite superhero shows when the brat climbed up on his chest, squished Katsuki’s cheeks together, and kissed him. Right there. Smack dab on the lips. Katsuki pulled away, horrified, nearly knocking Izuku down as he sat up. “Deku, what the fuck!” he whisper-shouted.
“Bad word!” Izuku said.
Katsuki put his hand over Izuku’s mouth and leaned forward again. “What the—what are you doing, you goddamn nerd?! Don’t do that!”
Why not? The child’s words were muffled but Katsuki knew what he was asking.
“Because it’s wrong. Don’t do things like that, Izuku,” he said, removing his hand from Izuku’s mouth. His cheeks hurt because for some godawful reason he was blushing about a fucking kid kissing him on the lips. It wasn’t a real kiss, sure, but it was fucking weird and Katsuki wished that stupid kid had never done it. “Where did you even learn that, you weirdo?”
“Mama and papa do it,” he said. Izuku did not struggle when Katsuki pushed his head down against his chest and began stroking his hair to soothe him. “And I saw it on TV…”
“That doesn’t mean you should do it,” Katsuki scolded.
“But I really love Kacchan and that’s what you do when you love someone, right?”
Katsuki could hardly hold that fierce look in Izuku’s big green eyes. He sighed, wondering how best to explain this to the fucking brat without making him cry. “It’s what adults do when they love each other,” he said. The wording felt oddly unnatural, but he didn’t feel like thinking any more about it. He wanted the conversation to end, despite knowing that Izuku didn’t really understand what he had done, or what being an adult meant necessarily, or love. Or anything. He was a kid, it was natural for him to be curious like that. It had been nothing but an innocent little kiss, yet Katsuki couldn’t get the feeling to go away.
“So I can do that when I’m a grown-up?” Izuku asked.
His naïveté physically hurt Katsuki. Right in the fucking gut.
“Yeah, I guess,” Katsuki said.
“But I love Kacchan now and I wanna. Please, Kacchan? Please?”
Izuku prolonged the vowels in his final plea until Katsuki had to cover his mouth again to keep him from waking his mother up. This kid, this fucking kid.
“Okay, fine. But only once. It’s really not okay to do that, do you understand, Izuku?”
“Yeah…”
“Then do as I say.”
“Okay.”
Izuku smiled all big like he did whenever Katsuki took him to the ice cream shop. His clammy little hands clapped over Katsuki’s cheeks, squishing them tightly together so his lips puckered. Izuku giggled, tilting his head this way and that as he examined Katsuki like one of his finely-crafted, Play-Doh All Might sculptures.
“Kiss!” he said, imitating none other than Recovery Girl as he leaned in close and kissed Katsuki’s lips. When he pulled away, his cheeks were a rosy red and his green eyes shone brightly. His childish gaze fell shyly as he leaned forward against Katsuki’s chest, overcome with another fit of quiet but happy giggles.
Katsuki felt wrong. He held the boy closer and shoved his nose between Izuku’s shoulder and neck and inhaled, smelling the sweetness of his shampoo and a hint of dirt from when he probably went to the park earlier that day.
“Time for bed, Deku,” he whispered hoarsely. Cottonmouth. Izuku slid off his lap, grabbed his hand and led Katsuki upstairs with a little skip in his steps.
Katsuki mentally kicked himself after putting the brat to bed and locking the door to Auntie Inko’s place.
What the fuck just happened?