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Izuku had intended to complete his math homework for the week and revise his English notes, but he'd invariably gotten caught up in hero studies, scribbling in his latest notebook and mumbling to himself for an hour as he followed the latest videos on Hero News. When he glanced at his watch, it was only 8:15, but he still wanted to shower before bed and prep a protein shake for himself to have in the morning, so he packed up to leave the study room.
On his way back upstairs, Izuku passed through a lesser used common space in the dorm. It was really just a nook on the way to the south stairwell that had a cozy window seat.
As Izuku went by tonight, though, he did a double take, noticing someone slumped in the window seat and snoozing underneath their athletic jacket.
He walked closer to the apparently sleeping figure.
They didn't seem to be hurt or anything, but, with their gym gear scattered on the floor around them, Izuku thought maybe they'd gone at it too hard during their workout or something.
"Um," Izuku approached. "Everything good over here- ?"
There was a soft snore from beneath the jacket, and Izuku cut himself off when it dawned on him that the dozing classmate was Kacchan.
The gym bag, as he looked at it again, was unmistakably Kacchan's trademark orange and black, and Izuku now noticed some blonde hair peeking out from beneath the jacket.
Kacchan was curled in a ball on the cushion of the window seat, breathing evenly.
Izuku was aware without even really needing to think about it that Kacchan would scream obscenities in his face if he woke him up. But. Izuku figured the blonde would probably be even more disgruntled to discover later tonight that he'd fallen asleep in the hallway.
It would be the polite thing to do to nudge him awake now.
Izuku reached out gently, being careful not to startle Kacchan. He pulled the jacket away from his friend's face, and what he saw- shocked him.
Moreso, though, Izuku felt a huge rush of unexpected nostalgia and affection. Kacchan was sucking his thumb in his sleep. Aww.
It was just like when they were kids.
Kacchan always denied it for obvious reasons, but to Izuku and his family, Kacchan had been known to suck his thumb well into being nine or ten years old.
He would also have spells where he'd act really... babyish around Izuku around that age, but then he'd always act like he didn't remember it.
Izuku had stopped seeing him much at all after that time, except for at school of course. He guessed he'd assumed over the years that Kacchan had to have grown out of that behavior for good at some point. And at UA they were always so busy, being slammed with mission after mission, it never even occurred to him to remember these things about Kacchan.
Now, seeing this at seventeen, Izuku was taken aback, sure. A little uncomfortable, even.
But when he got past the oddness of seventeen year old Kacchan still sucking his thumb, Izuku was willing to be totally honest. He thought Kacchan looked cute. His heart was maybe even melting just a few moments after the initial shock wore off. He practically put his hand to his chest and sighed.
His intent was to wake Kacchan up, though, not watch him sleep or even carry him up to his bed.
Izuku replaced the jacket that had been giving Kacchan privacy and then stepped back several meters before clearing his throat, "Kacchan!" he exclaimed loudly, "Is that you?"
Kacchan sprang up from his curled position urgently and looked all around him to collect his bearings. Izuku breezed past him to the stairs, not wanting to give him too much unwanted attention, and called out, "Night!"
Thankfully, Kacchan remained totally unaware of what Izuku had seen. The fact that Izuku was still standing was proof enough of that. As he waited in line in the cafeteria, Izuku grabbed his bottom lip and muttered, deep in thought.
He and Kacchan had had playdates since they were four or five—barely in kindergarten—and, even after Kacchan had publicly declared that Izuku was uncool, they would still play heroes constantly when it was just the two of them. They'd have sleepovers at each other's houses.
When other kids from their class weren't around, Kacchan was often very kind. In a Kacchan kind-of-way, of course. For instance, he'd let Izuku have the better or newer versions of action figures and dress-up costumes, saying they were lame or that he was happy with the dingier ones because they were his favorite. He'd not completely blow up when he lost to Izuku in Nintendo—even going as far as to say Izuku had played well—and he never failed to ask his mom to make them snacks or even to make them himself.
They probably played heroes the most, but they'd played other make believe games too. Some days, they played house. And, when they played this particular game, Kacchan always wanted Izuku to be the mom or dad, and he wanted to be the baby.
And, here's the thing, Izuku knew even at nine years old that Kacchan would have been mortified had anyone found out about their game, but Izuku? He didn't mind it. It hadn't even occurred to him to be judgmental. He was implicitly just kind of glad that Kacchan was able to let Izuku be there for him when playing pretend because he was otherwise always so stubborn about receiving help–
"Move it, nerd!"
Izuku jumped and looked to see Kacchan standing behind him, grumpy.
Kacchan raised an eyebrow and grunted, "You gonna move? You're holding up the damn line."
"Sorry!"
Izuku quickly got his food and returned to his usual table. His train of thought might have been interrupted for the moment, but it was definitely to be continued...
Weeks later, Izuku had actually all but forgotten about the thumb sucking incident. It had been cute, sure, but it didn't really change anything in his day-to-day. Except, sometimes, he would look over at Kacchan and those old memories would surface. This was… different… from their previous years in UA.
If he spotted him staring, Kacchan would ask him, loudly, just what the hell he was looking at. Which was fair. Izuku would then push the thoughts from his mind and move on. Kacchan snuggled cutely and at ease, suckling on his thumb like a baby without a care in the world was a warm, fuzzy picture, but it wasn’t all that consuming for Izuku, really. They ran in different circles, hung out with their respective good friends, and Kacchan really was the same old Kacchan this year, secrets or not.
With the whole incident far from his mind one evening, Izuku was struck completely still when he left Shoji's room after working on a partner project. It was Sunday, approaching six o clock, and it really hadn’t been all that restful a weekend. Most students in their class used their weekend time to get in even more training or studying. Yaoyorozu usually had to pre-plan a class hangout in order to get anyone to actually take it easy on the weekends these days.
But Izuku, brain fried, wanting to just grab some snacks and crash on his bed, had to stop short in the hallway. He could swear he'd just heard a small child whimpering.
Eri… was too old for that. And there was no reason Izuku could think of that she or any other child would be around the dorms tonight.
Izuku froze and listened. Could there be a villain nearby? Was he recently struck by some kind of quirk that caused hallucinations?
Izuku shook the thought from his mind. Stranger things had happened, but that was still pretty ridiculous.
Izuku continued to wait, and, sure enough, he heard the cries again. They grew in volume and intensity a bit, and Izuku was subconsciously not surprised that they grew more obvious the closer he got to Kacchan's door. A part of him just knew.
The thing to decide now was what the heck to do. Did he dare open the door and face whatever was on the other side? Whatever mood Kacchan was in?
A heartbreaking whimper followed, and Izuku tried to turn the knob without thinking. He had to check on him. That was final.
But the door was locked. Of course it was. Damn.
“Kacchan?” Izuku knocked lightly, ”Kacchan, can I come in?”
The cries cut off abruptly, and Izuku heard some shuffling. Izuku was patient, but three then four minutes went by, and he wasn’t sure if he should just take the hint and walk away.
Unable to actually make his feet move, Izuku waited a little longer, and he was so relieved he had. The lock clicked open.
When Kacchan didn’t answer the door, Izuku knocked again, “Kacchan?”
A soft… grunt… maybe?
“Kacchan, I’m about to open the door.”
Izuku did, and it ran right into Kacchan, who was curled up and sniffling on the floor, his face buried in his arms so Izuku could only see his cowlicked blonde hair and none of his expression.
Izuku quickly closed and locked the door again before dropping down beside his friend. “Kacchan,” he reached out a hand. When it wasn’t swatted away, Izuku placed the hand on Kacchan’s back and began rubbing slowly.
It could have been one minute or five, but Izuku gradually inched closer and closer and got less hesitant with the backrub. When it got to the point that Izuku was practically holding Kacchan, that was apparently all it took for Kacchan to totally unravel and begin bawling inconsolably in Izuku’s arms.
Kacchan buried his face in Izuku’s neck and clung to his shirt, moving willingly into Izuku’s lap when he tugged him. Izuku bundled him up, like he would any friend—or even civilian for that matter—and gave him comfort, rocking him and shushing him gently.
It’s just. Kacchan wasn’t any other friend. And he definitely wasn’t a stranger.
Whatever was going on, Kacchan wasn’t operating as his normal self. No way would a Kacchan with all his faculties, not under any quirk influence, fully aware of his actions, allow himself to be cradled by Deku of all people.
Oh. And he definitely wouldn’t stick his thumb in his mouth and start suckling needily while doing it either.
So something was off. And Izuku was just going to… roll with the punches he guessed. Punches he wasn’t entirely sure wouldn’t become physical by the end of this when Kacchan came back to himself again.
Kacchan had started to slump towards the floor, sucking his thumb, eyes watery, and still grasping for purchase on Izuku’s shirt, so Izuku hiked Kacchan up a little higher to hold him more comfortably against himself, and that’s when he brought a hand underneath Kacchan’s butt to lift him.
Izuku felt the wet squelch of the diaper immediately in his hand, and, if that weren’t enough of a tip off, the ear-piercing wail Kacchan let out would have been.
“Shhhh, shhh, it’s okay, Kacchan,” Izuku soothed. When Kacchan made to scramble away, presumably to hide his mess, Izuku just kept him close on his lap, urging him to quiet down.
“It’s okay,” Izuku went on, “No one’s mad at you. You did exactly the right thing, you’re alright.”
Izuku eventually had to stand up with Kacchan in his arms to keep his legs from falling asleep too badly. He lifted Kacchan easily with One for All and kept the blonde’s head against his shoulder, still whispering sweet nothings in his ear and encouraging the thumb sucking as self-soothing.
Izuku bobbed, and rocked, and paced, occasionally stroking a hand through Kacchan’s hair or down his back.
Kacchan settled, and then it was just the two of them, still tightly pressed together as Izuku bounced them in the room’s almost silence.
Izuku took the opportunity of a calm Kacchan to pull the curtains and turn on the light. Soon after, Kacchan became restless and wriggly in his arms. He seemed less distressed now, though, and more curious.
Izuku pulled back to see what he might be trying to communicate. Kacchan rubbed at his eyes and snot-stained face and looked up. When he saw he had Izuku’s attention, he nudged Izuku’s arm and pointed towards his closet.
Izuku got the message, but he turned to Kacchan’s nightstand first for a couple of tissues. He grabbed them, then whipped around again to double check that he had in fact seen an adult-sized pacifier with a lion decal next to the tissue box. The boy in his arms demanded his attention again, though, by squirming, so Izuku turned back, bounced him into a better position, and then wiped at the boy's face with the tissues.
When he was satisfied, he turned to grab one more tissue from the box and held it below Kacchan’s nose, instructing him to blow. He did, but it was poorly controlled and messy, leaving Izuku with yet more snot to mop up all around his face and a whiny Kacchan protesting this.
Izuku chuckled at him, causing the blonde to pout, "See? All better now." Kacchan didn't look like he thought so, but the pout was cute.
Kacchan kicked his legs and strained towards his closet again, so Izuku carried him over there to find whatever he needed. When Izuku slid the door back, he only saw clothes hanging neatly at eye level, but then he followed Kacchan's gaze to the floor and a partially opened cardboard box below the clothes.
He crouched down and opened the box fully. There was… a lot of… supplies? Baby and toddler things. Toys, stuffed animals, teethers, some bibs and rags with cute patterns, clothing items, and multiple packs of diapers and wipes. Where to begin?
Kacchan got him here, but now he looked a little far away in his eyes, lost and helpless and waiting for Izuku to do the rest.
Izuku sighed. "Here, it's okay, little one," he cuddled him closer. "You look like you'd like this stuffie," Izuku said, handing him a baby-soft lion plush. Kacchan latched onto it and brought it to his face with the hand not in his mouth. Izuku had to smile again.
"Okay, the first thing we have to do is get you changed." Kacchan blushed and hid his face, peeking out just barely from behind his lion. Izuku found it cute that Kacchan could let Izuku feel his wet diaper for ten minutes but apparently getting changed out of it was embarrassing.
Izuku read the various labels on the diaper packages in the box, and, sensing how wet Kacchan was, picked the thickest, most absorbent kind. He grabbed a bath towel from the closet's top rack and went to lay it on Kacchan's bed.
Kacchan somewhat resisted being set down, but his squirms were weak and uncoordinated. Izuku thought he must be more uncomfortable laying on his back, exposed, but there wasn't really another option.
Izuku pushed up the plain undershirt Kacchan was wearing to get it out of the way, but he noticed it was a bit worn and had drying snot in several places. Kacchan might not have changed out of it in a day or two, so Izuku opted to remove the shirt completely. Kacchan whimpered and protested at his now bare chest being exposed to the air. Izuku hushed him with a laugh which earned another disgruntled pout. That look just made Izuku laugh harder, but he tried to keep it contained for Kacchan's sake.
Kacchan hid his face with his lion dramatically when Izuku removed his thin cotton shorts and put Kacchan's soggy diaper on full display. He kicked and whined and stuck his lion's foot in his mouth. Izuku had a sneaking suspicion this is exactly what he wanted though. He smiled at Kacchan's antics a bit. They'd done pretend diaper changes when they were still pretty little, and there was the time Izuku held Kacchan's hand to go tell their preschool teacher the blonde boy had had an accident. Izuku had helped keep Kacchan calm while the teacher replaced his training pants, but this was Izuku's first time doing the real thing.
He thought he understood what to do well enough. Being a hero, he often went into situations he'd never faced before, and he'd always been able to keep his cool and figure it out in the end.
Izuku undid the tabs and removed the wet diaper, still amused by Kacchan's beet-red and hidden face. The little boy sucked his thumb harder to keep distracted.
Izuku grabbed a spare trash bag from the small bin next to Kacchan's desk and tied the diaper inside it before throwing it in the bin itself. Izuku picked up a pack of wipes from the closet next and started cleaning up Kacchan's private area.
Kacchan cried out and tried to turn over the second the wipe hit his skin. "Sorry, that's probably a bit cold, huh, buddy." Izuku removed the wipe and tossed it. "Maybe you'd like a bath? Would that be good, baby?" Izuku cooed his words in a baby voice without even planning to.
Kacchan made a happy sounding noise at the mention of the bath and Izuku's new nickname for him. Izuku chuckled. He couldn't seem to stop.
He drew Kacchan a bath and added some bubble bath he found underneath the sink, then he went to go carry his physically adult-sized baby into the bathroom.
He and Kacchan were about the same height now, Izuku having caught up and Kacchan staying the same. In a similar fashion, Izuku had bulked up further due to One for All and Kacchan was now slighter in comparison. He wasn't by any means the smallest or lightest, but Izuku thought Kacchan might appreciate it if Izuku acted like he was, picking him up like he weighed what a real baby would instead of the 160 or so pounds of a leanly muscled teenager. He thinks Kacchan approved.
Kacchan leaned his naked form outside of Izuku's arms eagerly to be put in the bath, and Izuku washed him lazily, letting him soak and play with the bubbles until he was bored of it all. Kacchan raised his arms to be taken out, and Izuku rushed to grab the towel they'd left on the bed.
He sat Kacchan on the edge of the tub to dry him while the water drained, and soon they were heading back into the bedroom so Kacchan could be laid out again.
Izuku thought some of the baby lotion he'd found in the bathroom would be a nice touch, so he soothingly rubbed it over Kacchan's skin before diapering him up nice and snug. Kacchan sucked two fingers contentedly the whole time.
Looking at the cute picture Kacchan made laid on his back on the bed in nothing but a soft white diaper, Izuku thought there was just one touch missing, so he gently removed Kacchan's fingers from his mouth and gave him the cutesy lion pacifier to suckle instead. The baby closed his eyes and hummed around his pacifier blissfully. He sucked greedily now, the little lion decal bobbing up and down.
Izuku had an idea to grab something from his room, but he wanted to assure Kacchan he'd be back first.
"Hey, baby. Sweetheart." Kacchan blinked up at him. "I'm going to go to my room for something, but I'll be right back, okay?"
Kacchan looked unsure of this, but he eventually nodded that he understood.
Izuku returned just seconds later as promised with something special he was really hoping Kacchan would like.
"Look at this, buddy!" Izuku tapped Kacchan's bare chest a little to grab his attention.
Izuku was holding out the limited edition All Might collectible shirt he'd waited in line for over six hours to get this past summer. Izuku knew Kacchan would have waited in line too, but he was on a training mission at the time. Kacchan had tried to be subtle, but Izuku noticed every single envious gaze Kacchan shot his way the times Izuku'd worn the shirt on outings or in a common area. Izuku absolutely would have bought two or three had it been allowed, but they were one per customer. He kicked himself later for not having his mom stand in line with him so he could've gotten one for Kacchan.
Seeing the shirt, Kacchan's eyes lit up. He babbled excitedly and tried to sit himself up but of course couldn't in his babyish headspace. Izuku smiled brightly, so proud he could make Kacchan excited like this. It was an even better reaction than he'd been hoping for.
Without inhibitions or needing to be cool, Kacchan made grabby hands and bucked excitedly to be put in the shirt. "Okay, okay, hold on," Izuku chuckled.
Izuku sat Kacchan up and slipped the shirt over his head, maneuvering the blonde's arms where they needed to go. Pacifier still in his mouth, Kacchan absolutely beamed when he was dressed, and he bounced his diapered bottom on the bed excitedly.
"You really like that, huh?" Izuku laughed and ruffled his hair. "You look so cute!"
The t-shirt was slightly big on Kacchan but not so big that it hung below his waist, so his diaper was still very visible including the line that served as a wetness indicator, so Izuku could be sure to change him if he wet himself again.
"What should we do now, baby boy?" Izuku asked in his over-the-top baby voice. "Toys?"
Kacchan shook his head and yawned.
"Sleep?"
Kacchan shook his head again, looking annoyed that Izuku couldn't read his mind. Izuku laughed.
"Want me to read you a story?"
There it is. Kacchan smiled as a yes.
"Okay! Let's go pick one out!" Izuku scooped Kacchan up and brought him over to his box. He sifted through it until he could pull out three choices for Kacchan.
He pointed at the first, "This one?" Kacchan shook his head. Izuku tried the second, then the third, and he laughed when Kacchan had scowled and shook his head no all three times.
"Then what am I going to read to you, sweetheart?"
Kacchan made a gesture, spreading his arms apart past where the books lay on top of the box.
"Oh, I'm going to read ALL of them for you?" Izuku asked, exaggerating his voice again. Kacchan giggled and nodded yes. "Okay," Izuku said easily. Caught up in the cute moment, Izuku impulsively kissed the blonde's temple without meaning to. He froze for a second, but Kacchan didn't seem to have noticed the possibly boundary-crossing show of affection, and Izuku breathed a sigh of relief and brought them over to get comfy against the pillows on the bed.
Izuku had Kacchan cuddled to his side, the baby still sucking his pacifier and holding his lion. They were in the middle of the second storybook when they heard a key push the lock in the door.
Both perked up. Izuku was unsure of what was going on, but Kacchan seemed totally unconcerned.
The next thing Izuku knew, Kirishima was coming through the door.
"Mmnnnh!" Kacchan made a happy grunt and threw himself into Kirishima's arms, wrapping his legs around the sturdy hero's waist. Kirishima belatedly noticed Izuku there, dumbstruck and still holding the picture book open on the bed. Kirishima looked just as shocked.
Kirishima opened his mouth like he was about to say something to Izuku, but Kacchan koala-clung to his red haired boyfriend further, nuzzling him aggressively just to make sure he could take up all of Kirishima's attention for the moment.
Kirishima seemed to have accepted Izuku's presence for the time being, and he began holding and nuzzling his boyfriend back, giving him the attention he craved and baby talking to him softly, presumably like he would if Izuku wasn't even there.
"Baby," Izuku heard Kirishima say, addressing Kacchan and holding him tight, "you could have just told me if you needed me to come home." He kissed Kacchan's cheek and forehead and nose several times as they rocked. "My parents and I didn't even have anything going on this weekend." The red head's hair was down in a low, scruffy ponytail, and he was wearing comfy looking sweats.
Kacchan shook his head against Kirishima's chest and made a noise of disagreement.
"You're so stubborn," Kirishima said fondly as he rocked his baby, peppering kisses into the blonde's freshly clean and soft, sweet smelling hair. Izuku saw Kirishima take a less than subtle sniff. He looked at the expression on Kirishima's face, and he just seemed so happy to have Kacchan in his arms again. The two cuddled like they'd been apart for a lot longer than a weekend.
Izuku felt an awkward blush creep over himself as he sat there immobile and watching the whole tender scene unfold. He really shouldn't be here for this, but he couldn't pull his eyes away.
He'd known 'baby Kacchan' for all of a couple hours, and he was already jealous of Kacchan's boyfriend of two years! For standing there and giving Kacchan exactly what he needed of all things. For knowing the blonde best. Kirishima was Kacchan's everything and had been for a while, so of course he would know Kacchan best. Izuku couldn't believe himself and his possessiveness.
But Izuku considered further. Maybe his bond with Kacchan when Kacchan was... like this felt more like it had lasted their whole lives rather than a couple of hours.
Izuku finally got himself put back together enough to start unfolding from his place on the bed slowly. He was intending to sneak out and finally give the other two some privacy, but Kirishima stopped him on his way out.
Kacchan was happily lazing on Kirishima's chest.
"Uh, hey, man," Kirishima said, rather quietly and awkwardly for him. His voice was a little scratchy and rough in that very Kirishima way. "You don't have to go… if you wanna stay."
Izuku wasn't sure. His mind couldn't be less made up.
"I really appreciate you looking after him today," Kirishima continued, growing bolder. "Did you know before… or?" Kirishima asked, not needing to specify what Izuku might have known about. He just gestured to Kacchan in his current state.
"No." Izuku said immediately. "But…" he started after a pause, "but when I did find him–a couple hours ago, by the way–a lot of stuff from our childhood suddenly made sense."
Kirishima nodded. "Okay." Then, after a moment, "You were good to him? Like you accept–" Kirishima cut himself off. "It's just he's been through a lot of traumas and–"
"Kirishima," Izuku said sincerely, "Of course."
"I know, I know," Kirishima said a little sheepish, "Sorry, I just had to ask, y'know?"
"Yeah," Izuku understood.
"Here, why don't you take him for a second."
Izuku was startled at suddenly being handed two armfuls of Kacchan.
"I'm going to make him something to help him fall asleep. He'll be back to normal in the morning since we have school, but I've missed being with him like this."
Izuku nodded. He also wasn't going to turn down more time being offered with a sweet baby Kacchan.
Izuku turned off the overhead light in favor of the desk lamp and walked the room with Kacchan in his arms. He'd whined momentarily when Kirishima'd passed him over, but now he was content to suck his paci and stare off into space until his boyfriend came back. Izuku felt the baby wet himself, his diaper growing warm against Izuku's stomach, but Izuku just pretended like he didn't notice and kept up his pacing.
Kirishima returned with a bottle of milk in his hand. It was small-ish but certainly larger than would fit a real baby. He reached out to take his boy back, and Izuku tried not to show that he wanted to be greedy and keep holding him.
When Izuku handed him over, he noted, "He's wet. Just while you were gone."
"Okay," Kirishima smiled, "I'll change him after his bottle."
Izuku nodded. "I'll just go then," he said, but he didn't move quite yet.
Kirishima sat against the pillows with his baby across his lap. He removed the pacifier from Kacchan's mouth to give him the nipple of the baby bottle instead, and Kacchan began drinking his bottle steadily, a little milk dribbling down his chin that Kirishima wiped up with his hoodie sleeve. Kirishima smiled warmly down at him, holding him cradle-style in his arms, wet diaper and all.
Izuku picked up the lion plushie that had landed on the floor in a last ditch effort to linger. He placed the lion on the bed and said, "In case he needs it later."
"Thanks, dude," Kirishima said. "Really, you're the best. And hey-" Kirishima might have noticed Izuku's reticence to leave, "He might want you to, y'know, like babysit again."
"Really?" Izuku asked.
"Yeah, he's mentioned it before, in more of a toddler headspace. I must not be a very fun villain to defeat during playtime. He seems to think you'd be much better at it," Kirishima shrugged.
Kirishima returned his attention to Kacchan, and Izuku left the room soundlessly, but for the next week, he walked around with the biggest smile on his face.