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Izuku had gotten back a bit late from a long day of field training, so he was alone in the locker room when he finally got to take his gear off, take a shower, and change back into casual clothing. It was times like this when he was glad they lived in dorms now, since he wouldn’t have to catch a later bus back to his neighborhood.
As he left, he pulled out his phone to start browsing his favorite hero forums, so he didn’t see All Might walking up behind him.
“Young Midoriya!” the man said, putting a hand on his shoulder.
“Ahh!” Izuku jumped, but quickly calmed himself, turning his scream into a stuttered, “A-a-all Might!”
“Haha, yes! I was looking for you,” he explained, suddenly looking a bit awkward.
“Um, is something wrong?” Izuku asked, slipping his phone into his back pocket.
“Well, you see, there was a little bit of an accident during Bakugou’s field training today,” All Might started to explain.
“Oh my gosh, is Kacchan okay?” Izuku blurted out, his eyes growing wide with concern.
“I’m fine,” a little voice said, drawing his attention to the ground. Behind All Might’s leg, a little blonde kid stood staring up at Izuku with big, red eyes. It took Izuku a second, but then he realized the kid looked exactly like Katsuki did when he was three.
“Well, yes. He’s not hurt or anything, but there was quirk-related accident that turned him back into his younger self. Much, much, younger self,” All Might explained.
“I s-see,” Izuku nodded, still a bit flabbergasted.
“Are you Izuku-chan all grown up?” the little Katsuki asked.
“Um!” Izuku felt his face flush up at how cute the kid was, but forced himself to calm down and answer the question. “Yes, that’s me!”
Katsuki smiled wide and said, “I knew we’d both get into UA! This is so cool!”
Izuku started laughing then, and he realized that Katsuki at this age – before he got his quirk – still thought they were best friends and wanted to be a hero duo together.
“Oh, did you now?” All Might asked, cocking an eyebrow at Izuku in question.
Izuku nodded, trying to think of how to explain it without confusing the kid, and then whispered, “This was before he got his quirk.”
“Hm?” Katsuki looked up, confused.
“Nothing! Just that… you’re right!” Izuku said, putting on a smile and kneeling down so he could better talk to Katsuki. “We both got into UA, and we both got super cool quirks!”
“Can you tell me what mine is?” Katsuki asked with stars in his eyes.
“Of course I can! But, can you let All Might finish explaining what happened to you to me?” Izuku asked.
“Okay,” Katsuki made a pouty face, but relented.
Izuku stood back up and let out a little sigh.
“Right. Well, I thought you might be the person to talk to, since you’re the only one who knew him at this age,” All Might said.
“True. But, don’t you think we should just send him back to his parents until this wears off? They’ll know a lot more than me,” Izuku laughed awkwardly.
“Well, here’s the thing. The quirk should wear off in less than twelve hours, so it would be a bit of an inconvenience to do that for such a short amount of time. Instead, the other teachers and I thought maybe you could just… babysit for the night? He’ll be back to normal in the morning, after all,” All Might said, making a pleading face towards Izuku.
“I…” Izuku bit his lip, thinking about it, but All Might didn’t wait for him to agree.
“Great, thank you, Young Midoriya! Here’s everything we bought at the store for him on the way back. Good luck!” He handed Izuku a plastic shopping bag and basically bolted, leaving him with the toddler.
“W-wha…!” Izuku’s mouth flapped helplessly, but eventually he sighed and shook his head. This was fine. At least Katsuki wasn’t four. Then he’d have been a nightmare.
—
They were practically swarmed as soon as they entered the common room, and between their classmates’ general confusion and ogling over how cute Katsuki was as a kid, it took awhile for Izuku to finally finish explaining.
“Wait, why did All Might ask you to take care of him?” Ochako asked. “Doesn’t that seem sort of… counterintuitive?” she tried to put it lightly.
“Well, I am the only one who knew him as a kid,” Izuku rebutted.
“But wasn’t your relationship bad back then, too?” Kirishima asked.
“No! No,” Izuku tried to talk over him. “Kacchan and I were… are friends,” he added, glancing nervously down at Katsuki, who was currently gazing out quizzically at the circle of teenagers around him.
“Uh-huh,” Kaminari said sarcastically, raising an eyebrow.
“It’s true! Right Kacchan? You and I are friends, yeah?” Izuku looked down at the kid sympathetically.
“Duh. Izuku is my best friend, obviously,” Katsuki said, still looking puzzled.
“Huh. Who would have known,” Kaminari shrugged.
“Well, if you need any help with him, you can always ask us,” Kirishima said, grinning enthusiastically.
Ochako cringed and whispered to Izuku, “I’m not so sure that’s a good idea.”
Izuku chuckled.
“Don’t worry. If worst comes to worst I can always call my mom,” Izuku shrugged.
“Or my mom!” Katsuki offered, then seemed to second guess himself, putting a finger to his chin. “On second thought, call Auntie Inko. She’s nicer.”
“Oh my god, he calls your mom auntie?” Mina gushed.
“Uh… y-yeah,” Izuku nodded.
“That is so freaking cute!” she put her hands up to her cheeks, and Katsuki rolled his eyes.
“Can we go now? I don’t know how much more of this I can stand,” he huffed.
“Ah, there’s the Bakugou we know,” Kaminari joked.
—
As soon as Katsuki walked into Izuku’s room, his eyes widened in delight.
“You have so many cool All Might posters!” he said, practically shaking with excitement.
“Yup! Do you want to see my figurines?” Izuku asked.
“Yes! Yes! Yes!” Katsuki was jumping up and down, and when Izuku started taking them down from atop his dresser, Katsuki made grabby-hands at him. Izuku smirked a bit at the realization that Katsuki was a bit selfish back then too, expecting to just be handed all the toys he could want without even saying please, and yet Izuku felt compelled to give him what he wanted. At least it was just that innocent, little-kid sort of selfishness; he knew Katsuki was capable of much worse… and so much better.
Shaking his head to clear his thoughts, Izuku refocused on the kid playing with his All Might figurines, kneeling on his All Might rug. He was completely occupied. So much for this babysitting thing being hard.
Izuku grabbed his homework and sat down at his desk, getting to work while Katsuki’s high-action superhero rescue sound effects drifted in one ear and out the other. After about an hour though, he suddenly fell silent.
Izuku looked up from his homework when he noticed it, not sure how long Katsuki had actually been quiet, and turned around to check on him.
Katsuki was still kneeling on the floor, an action figure in each hand, but he wasn’t playing. He was just staring at the ground looking frustrated while tears formed in the corners of his eyes.
“Kacchan,” Izuku said, scrambling down out of his chair to kneel in front of him, putting a hand on each of his shoulders. “W-what’s wrong? Are you okay?”
“Mn,” Katsuki bit his lip and looked away.
“Ah, I–I’m sorry I ignored you! Do you want me to play with you?” Izuku asked frantically.
“That’s not what’s wrong, stupid,” Katsuki pushed at his chest weakly, and Izuku let go of him in reaction. It seemed that wasn’t what Katsuki wanted though, because suddenly he fell into Izuku’s chest and started to cry quietly.
“I just don’t get it,” he forced out.
Izuku’s chest got tight, and he let his arms settle gently around Katsuki’s tiny torso, trying to soothe him.
“Why do they all think we don’t get along? Wha… what happened?” he practically wailed.
Izuku let out a stuttered sigh and chose his words carefully.
“I… I can’t lie to you. What they said is true. For a long time we… we didn’t get along at all. In fact, our relationship has only just started to get better again,” he admitted.
Katsuki pulled his head up and wiped at his eyes with the backs of his hands.
“But why? I had everything planned out! We were supposed to be together forever! I was supposed to make you mine by now!” he sobbed.
“Kacchan, I’m sorry but that just didn’t–” Izuku started, then suddenly went red as the words registered. “Wait, what?”
“Did you reject me?” Katsuki went on crying. “Is that why we don’t get along anymore?”
Izuku’s head was spinning.
“R-reject… what?”
“My confession!” Katsuki said it like it was obvious.
Izuku froze up. Katsuki went on crying and desperately trying to wipe his eyes, completely unaware of Izuku’s state of shock. When he had calmed down a bit, his hands settling in his lap and his head down to hide his puffy eyes, Izuku spoke again.
“Kacchan… let me get this right. You… like me? And when you say you wanted us to be together, you don’t just mean as a hero duo, but as… a couple?” he asked slowly and deliberately.
Katsuki nodded.
“Didn’t I explain it to you?” he asked.
“No, Kacchan. You didn’t. You… you never confessed,” Izuku broke it to him. Katsuki looked up, confusion written all over his face, and then back down again, where he put a hand on his chin.
“Then… did I… stop liking you? Or did you start dating someone else?” he asked, clearly trying to parse it out.
“No. I mean, I don’t know about the first one, but I wasn’t dating anyone. Rather, I… well, the truth is I… I didn’t get a quirk. And when you realized I was quirkless, you started treating me like… like I was worthless,” Izuku bit his lip, not sure he should be telling the kid this.
“But… you have a quirk now?” he questioned.
“Yes, I, uh… look, I’m going to tell you this because the older you knows already anyways, but you have to promise not to tell anyone else, okay?” Izuku looked him in the eye, and Katsuki started nodding.
“I promise!” he said.
Izuku sighed, dragging a hand down over his face.
“All Might gave me his quirk. That’s why he’s… well, you know, retired, now,” he explained hesitantly.
Katsuki eyes widened, blinking slowly as he took it in.
“Oh! That’s why he looks so weird!” he said.
Izuku cringed slightly, but nodded.
“Well, then… everything should be fine, now. You have a quirk, and a really good quirk, too! So then… we can still be together, right?” Katsuki asked, suddenly looking unsure of himself.
“Uh… if that’s what you want,” Izuku nodded slowly, his features riddled with uncertainty; he simply had no idea what to say to him.
“Of course that’s what I want, I just said so,” Katsuki insisted, picking up Izuku’s figurines again and setting them all upright.
“Well, but… maybe you’ve changed?” Izuku said, then practically bit his tongue at his stupidity. The conversation was almost over and now he’d gone and started the debate again!
“Mm…” Katsuki considered it a second, then shook his head. “I don’t think so. I’m too stubborn to do that.”
Izuku gawked at that answer, completely unsure of how to respond, but Katsuki seemed convinced that that was the end of it. He’d gone back to playing without a care in the world. Izuku scratched his head, wondering if what Katsuki had told his was even possible – that he liked him – and yet he couldn’t deny the whole thing seemed very like him. He’d just gone ahead and decided Izuku’s future without ever consulting him, and then informed him of how it would happen without a care for Izuku’s opinion. He couldn’t help laughing, quietly, as he stood up and sat back down at his desk.
Was that why Katsuki was so mean to him after he found out he was quirkless? Because he’d ruined his plan? And was that why he’d been so mad when Izuku used his quirk for the first time? Because he’d made him abandon his life’s plan when he didn’t have to?
Well, he was pretty sure there was more to it than that, but since he’d just heard it from Katsuki himself, he had to believe it was true.
“Izuku-chan?” Katsuki asked.
“Hm? Yeah?” Izuku turned around.
“I’m hungry. Can we eat dinner soon?” he asked.
“Oh! Right!” Izuku checked the time and, seeing it was already half past six, led Katsuki downstairs to eat, settling back into his role as babysitter.
—
When it was time for Katsuki to go to bed, Izuku opened the bag All Might gave him to find a pair of red footie pajamas, a little tube of kiddie toothpaste with a small toothbrush, and a night light.
“Okay, Kacchan. Can you change into your pajamas on your own?” Izuku asked once he’d taken off the tag.
“Of course I can,” Katsuki said, snatching it out of Izuku’s hands.
“Okay, okay!” Izuku put his hands up. “I’ll wait outside. And then you’re gonna brush your teeth and go to bed, yeah?”
“Mm-hm,” Katsuki nodded, no longer willing to protest his bed time now that Izuku had informed him it was self-imposed. As Izuku waited out in the hall, he found himself chuckling at the thought of how easy it would have been to lie about that just to get the kid to cooperate, and yet it wasn’t a lie at all. Katsuki really did go to bed at nine nearly every night.
“Kay. I’m done,” he heard from the other side of the door after a few minutes. When he opened it, Katsuki handed him the clothes he’d been wearing before all folded up neatly, and Izuku couldn’t help smiling at the reminder that Katsuki had always been neat. Maybe less about him had changed than he thought?
“Alright. I’m gonna bring some books to the bathroom for you to stand on so you can reach the sink, okay?” Izuku explained, dropping the clothes in the bag and slinging it over his shoulder before he grabbed his textbooks.
“You don’t have a step-stool?” Katsuki asked, his cheeks a little red.
“Well. We don’t usually have anyone under fifteen in the building,” Izuku shrugged.
“Oh. Yeah. Okay,” Katsuki nodded, and they headed down the hall. As they reached the bathroom, however, another thought occurred to Izuku.
“Um. Can you… use the toilet on your own?” he asked quietly.
“Duh!” Katsuki said. “I’ve been potty trained for…” he paused, counting. “Five months!” he announced, proudly displaying the corresponding number of fingers.
“Right,” Izuku smiled and nodded, suddenly reminded of just how little Katsuki was. It cast quite a bit of doubt on his earlier… confession. Little kids have all sorts of ideas that never come to fruition. It’s just not realistic to think that at sixteen he’d still be following the life-plan he made at three. Though… if anyone were to do it, Katsuki might be the one. He was crazy stubborn and self-assured, after all, and if Izuku knew Katsuki well enough, he’d say it might just be possible.
But, that’s crazy, right?
“Okay. All done,” Katsuki said, drawing Izuku out of his thoughts.
“Oh, right! Let me just take my books back to my room, and then I’ll take you up to yours and tuck you in, okay?” Izuku said, smiling at him and offering his hand. Katsuki nodded and wrapped his little fingers around two of Izuku’s, walking back down the hall with him, and then up the stairs after a pit stop at Izuku’s room. Katsuki’s room was left unlocked by Aizawa, who had brought Katsuki’s clothes and bag back to his room after the incident, so they just walked right in.
Katsuki spent a bit looking at his room, mostly remarking at his own merch collection before he climbed up and settled into his bed. It was much too large for him, and when Izuku pulled the blanket up over him, he looked even smaller.
The other thing he couldn’t help noticing was that, despite his earlier protest, Katsuki did look tired now that he was lying down.
“Alright, uh…” Izuku looked around, then spotted an outlet next to the bed. “I’ll put your nightlight here okay?” he said, taking the thing out of its packaging and slotting it in. Katsuki didn’t say anything, he just nodded, and Izuku held in a tiny smirk at the thought that he was probably embarrassed by the fact that he still needed to sleep with one.
“Okay. Goodnight, Kacchan,” Izuku smiled at him one last time, then went to the door and turned off the lights.
Just as he did, though, Katsuki called out to him.
“Wait,” he said, his voice sounding smaller than usual.
“Huh?” Izuku turned around and walked up to the edge of the bed, kneeling down so he could look at Katsuki. “What is it?” he asked.
“Izuku-chan… if I confessed to you after all, what would your answer be?”
Izuku almost went pale with shock at how blunt the question was, but his face quickly softened back into a smile.
“I’d say that I love you too, Kacchan,” he whispered, and kissed Katsuki on the head. Katsuki grinned broadly, and it made Izuku cuckle. “But you have to confess when you’re big again, or I won’t believe it, okay?”
“Mm-hm! I’ll show you! We’re gonna be together forever!” Katsuki nodded enthusiastically.
“Good. Now go to sleep so you can wake up and do just that in the morning, yeah?”
“Yeah!” Katsuki rolled over, putting his head on his hands in a classic ‘I’m totally asleep’ pose. “Goodnight, Izuku-chan!”
“Goodnight, Kacchan,” Izuku smiled and left the room.
Once he was gone, though, his smile faltered.
Katsuki was going to remember that tomorrow.
He was going to know how he felt.
—
When Katsuki avoided him for the next few days, he couldn’t say he wasn’t surprised. It must have been embarrassing when he realized he’d divulged his childhood crush and even more mortifying to find out that Izuku reciprocated those feelings now that Katsuki was definitely, certainly, irrevocably over it.
At least, that’s how Izuku interpreted his silence.
It wasn’t until three days after, when they both happened to be in the kitchen at the same time in the evening – alone – that Katsuki felt compelled to speak.
Izuku was staring into the fridge having completely forgotten what he was doing now that Katsuki’s eyes were on him, but he slowly closed it, building up the courage to meet his gaze. He didn’t want the silent treatment to go forever, after all.
“Oi, Deku,” Katsuki said, finally queuing Izuku to really look at him. His hands were in his pockets, and his eyes were narrowed in focus, but there was a bit of warmth in his cheeks.
“Y-yeah?” he squeaked.
“You only said that to make me feel better, right?” came Katsuki’s question.
Izuku furrowed his brows.
“W-what? Said what?” he asked, his heart rate picking up.
“Tch. You know what I mean. Don’t play dumb,” Katsuki grumbled, turning his head away. Izuku couldn’t help but notice that the tips of his ears looked pink, and then he got it.
“Oh!” he said involuntarily, and then felt his stomach drop, understanding in an instant just how much this situation sucked. He could easily get away with. Katsuki was giving him an out – it would be so easy – and yet, he knew he couldn’t lie. He twisted the front of his shirt with his hands nervously, and then shook his head.
“N-no. I was telling the truth,” he forced out.
Katsuki froze. In an instant, his face worked through a range of emotions – confusion, denial, realization – and then he smirked, like he had an idea. Mortified, Izuku looked down at his toes and tensed up as Katsuki walked over. Katsuki was probably going to make tease him over this for years, wasn’t he? This was the end of their friendship, wasn’t it?
But then, Katsuki said something unexpected again.
“You said all I had to do was confess, right? And then you’d be mine?” he said, voice low and – if Izuku wasn’t crazy – almost sultry.
“Well, I… but that was… I didn’t think you’d…” Izuku sputtered, then gulped when he realized he wasn’t going to be able to form a coherent sentence.
“I’m only going to say this once, so listen up, nerd,” Katsuki said. Izuku nodded quickly, suddenly realizing how sweaty he was. “I like you. I have this whole time. And everything I wanted then, I want now. I want… I want you,” he said, his arms coming to rest gently around Izuku’s waist and his lips so close Izuku could feel his breath on his ear.
“I…” Izuku started, but found no words.
Katsuki pressed a kiss to his temple.
“Too surprised to respond?” he asked.
Izuku nodded and gulped, a bit of a shiver going up his spine. How was Katsuki making his voice so… so… sexy? Was he allowed to call it that?
“It’s okay. You already told me your answer,” Katsuki said pressing more kisses behind his ear.
“Y-yeah,” Izuku forced out, but his voice cracked. Katsuki chuckled, the low rasp of it making Izuku shiver again, and he decided that if words were going to fail him, all he had left was his actions, right?
And so, after a deep breath in for courage, he turned around and gripped Katsuki’s cheeks, preparing to kiss him, only to be stopped by the sight of how embarrassed Katsuki looked.
His face was bright red. Izuku didn’t even know it was possible to blush that much!
“Oh my god!” Izuku burst out laughing, all while still holding Katsuki’s face.
“What the hell are you laughing at?” Katsuki barked, grabbing Izuku’s wrists but not really trying to pull them away.
“It’s just, this whole time you were pulling off this whole… seduction thing, when in reality you were hiding your face because you’re just as embarrassed as me!” Izuku got out between giggles.
“I am not! You just surprised me,” Katsuki insisted, looking anywhere but at Izuku.
“Uh-huh. Sure,” Izuku rolled his eyes, then finally went through with his plan and pulled Katsuki’s face down for a little peck. Katsuki was startled for a moment, then kissed him back, their lips actually sliding together a bit as their faces tilted in opposite directions.
When they parted, Izuku sighed happily, letting his arms fall around Katsuki’s shoulders and his head onto his chest. They stood there like that, perfectly silent for a long time, and Izuku found that he couldn’t stop smiling.
The little kid was right.
He really was that stubborn.