Chapter Text
Katsuki Bakugo was on top of the world: he was the strongest and smartest pup in the playground, so it was only natural that the five year old took it upon himself to rule over the play area with an iron fist. He could do pretty much whatever he wanted as long as nobody cried, aware that parents would swoop in and ruin his power trip if that was the case.
He was currently jumping on the tallest part of the jungle gym, clutching an All Might action figure in his hand as he surveyed his little kingdom before throwing himself down the slide and laughing, ready to do it again.
"Kacchan! Kacchan! Wait for me!" A little voice called from behind him, running on knobbly little legs to catch up with him in the playground.
Katsuki sighed; Izuku was short and not very fast at all, so he could never keep up with him and his little pack of pups that wreaked havoc upon the playground whenever he was there. He was weak and would cry if anyone growled at him or even if they refused to share or play nice. He was annoying.
And yet, Katsuki stopped where he stood just long enough to let Izuku catch up with him and hold onto his hand.
"You're too slow." The blond pointed out right away with a glare that promoted the other pup to apologise again and pout a little bit.
Izuku had been part of his life ever since he could remember, his dad had even made a point of showing them pictures of the two of them as six month olds sitting next to each other with dumb baby smiles, so pretty much every important memory that he had involved the green-haired pup. Because of that, annoying as the other kid was, Katsuki couldn't just shake him off and leave him on his own (because Katsuki wasn't dumb, well aware that his dad would swoop in and tell him off if Izuku started to cry again).
Katsuki proceeded to drag Izuku along to the swings and make a point of showing off the fact that he could propel himself by folding and stretching his legs on the swing, basically glowing with pride as the other pup looked at him with awe and praised him for being so cool, even cheering for him when he jumped off the moving swing in a little act of daredevilry.
It was then Izuku's turn to go on the swing -because Katsuki was a civilised pup, thank you very much, he understood that turns needed to be taken even when lame people were involved- so he watched as the smaller pup climbed onto the swing and wiggled his legs fruitlessly.
"Kacchan, I can't do it." He whined.
Katsuki watched as the other boy failed at swinging and smirked for a moment at his own superiority before feeling light worry settle in his heart at the clear distress the other pup was feeling at being unable to propel himself on the swing. He let out a quiet grumble before stepping in and starting to push the swing for him, causing Izuku to stop whimpering and laugh, clearly enjoying himself and continuing in awe at how big and strong Kacchan was to be able to help him swing like his mama often did when they came to the park together.
He pushed his swing for a little while, eventually deciding it was enough and stopping his efforts to let the swing come to it's natural halt and let Izuku get off. He had not been expecting the other boy to jump off the swing and straight into running to hug him, overflowing with puppy gratitude.
"Aw, cute~" Mitsuki Bakugo cooed, apparently materialising out of nowhere to come make Katsuki flush and get embarrassed. "Is Izu-chan your omega, Katsuki?" She teased her son, prompting the blond pup to escape the hug and cross his arms while glaring and shaking his head no. Everyone knew that omegas were boring and yucky, and he wanted nothing to do with them.
The alpha woman had never been interested in having her little boy go through an elective anatomy scan to find out what her son's secondary gender was; in her opinion it wasn't really worth it, especially when it was an expensive test with new technology that had not been available when she was growing up. She and all her peers turned out just fine by waiting until puberty to find out what their dynamic was, so there was no real reason for the newer generation to know right from the jump. It was much more fun to keep on guessing and noticing all the little developments her puppy had.
Besides, people had been making accurate informed guesses on the gender of their babies for millennia based upon their temperament, likes and personality. Everyone knew the old wives' tales: if a pup got colds often and was sleepy in the mornings they would grow up to be omega, while a kid that was up and active since dawn and lost their top baby teeth early would grow to be an alpha.
Sure, these methods weren't foolproof and sometimes people got a surprise later in life, but come on: who in their sound mind would look at her grumpy and dominant early-riser that couldn't wait to get out and about to boss the whole world around and think he was anything other than a fierce little alpha?
On the other hand, little Izuku Midoriya was everything she ever thought an omega puppy was meant to be: he was sweet and cuddly, incredibly polite and very affectionate. In her opinion, little Izuku was a great influence on her angry hurricane of a son, so having both pups going to play-school together and playing with each other basically every day was a blessing for her. Katsuki was a demanding little monster that seemed to need constant attention and play in order to avoid mischief, so having Izuku around served as a way to keep her little hellraiser entertained enough to keep him from driving his parents insane. And god knows poor Inko needed a break and some time for herself now that her deadbeat alpha had fucked off to 'work abroad' when it became apparent that their pup was both omega and quirkless, a far cry from a winning combination.
Mitsuki took it upon herself to wrangle the pups out of the playground in order to take them back, which mainly meant having to chase and corner up her own devilspawn; little Izuku was obedient and went straight on to hold her hand when she said that it was time to leave the park, while Katsuki took it to mean that it was time to climb up the slide twelve more times until Mitsuki threatened to leave him in the park forever, to not feed him dinner and to throw his new All Might toy in the rubbish bin. The threat against his new favourite toy was enough to have Katsuki reluctantly drag himself back to his dad.
Eventually, she was able to get both little boys to hold hands (because Katsuki was angry at her and refused to hold her hand, but little Izuku had made a point to explain that 'we hold hands when we cross roads, Kacchan' and not even the angry little boy could argue against that) and walk them to Izuku's apartment building in order to hand the sweet little boy back to his mother's care and take her very own little hellraiser home, hoping that an hour in the park had been enough to tire Katsuki out to avoid a whole battle around bedtime.
As the years passed and they moved up from play-school to primary school, Izuku remained an ever-present feature of Katsuki's life: the whiny little twerp walked with him to and from school, followed him around the playground and class in general, did homework with him and even got paired up with him for most group assignments. He was there for birthdays, play dates and even the odd holiday, as his dad and Deku's mum had been friends since school and therefore were around each other the whole time. They lived close by as well, so having Deku be with him more often than not was just a natural consequence.
The relationship between the two boys was weird in exactly all the right ways interaction between children seemed to be. Both Inko and the Bakugos had often joked that the boys were the closest each of them had to a sibling, which was absolutely a good thing in their books given the many questionable things that were always said about the downsides of having a single child (Masaru and Mitsuki had always wanted more than one kid, but after the hell that raising stubborn Katsuki out of toddlerhood had been, they settled for just one). Izuku seemed happy to have an ever-present companion to play with, and heavens know that Katsuki could do with having another pup around to learn how to share, take turns and be less of a little shit when he didn't get his way.
Katsuki was dominant and bossy and a bit of an arse the whole time, but Izuku didn't seem to mind his lack of manners and would always react to him with the sweet smile that characterised that young boy.
Despite how vastly different the two boys were, their friendship was without a doubt centred around their shared admiration and obsession with heroism in every single way. Most young kids liked heroes, sure, but those two took it to a whole new level as each and every single one of their afternoons was filled with re-runs of cartoons featuring all the greatest heroes of the last century and playful reenactments of the greatest battles of their favourite heroes using action figures or cardboard props. The pair fought and bickered over all sorts of things, but they were both firmly in agreement was the fact that All Might was the best hero ever.
The one serious sore spot in their relationship was the fact that Izuku was quirkless and didn't quite grasp the fact that he could not be a hero that way. The conversation always came about the same way: Katsuki would brag about growing up to become the best hero ever and Izuku would chime in to say that he would too only to be shot down by the other boy. They would bicker back and forth for a while, with the conversation normally ending when Izuku rather diplomatically mumbled an okay that didn't really reach his eyes or his heart: he knew he was going to be a hero, but he had enough experience dealing with Katsuki to know it was in his best interest to not stay locked in that back and forth with the most stubborn person he knew.
Their friendship had its ups and downs, mostly tied to Katsuki's moods. Some days they would play nice together for hours, others would end quickly when he told the other boy to get lost and called him a dumb nerd or something of the like. They both knew Katsuki could be nasty at times, but Izuku found it always easy to forgive and forget and just keep on experiencing life by his side, letting the slightly older boy lead the way through play grounds, nature parks, school assignments and childhood milestones. Izuku just kept coming back every single day regardless of the unpredictability of Kacchan's explosive personality, basking on the good days and skimming past the bad ones as he continued to follow his lifelong friend through the sinuous roads of boyhood.
Katsuki was nine the day he first used the word bitch.
He had been minding his business as usual in school, his ego already boosted by the fact that he had gotten the highest score in their whole year in that one big maths test (because he was the smartest kid in school, and now everyone else had real confirmation to that fact). He was on top of the world and nothing could erase that smirk from his face.
“Kacchan! You did so good! You’re so smart!” Izuku praised him as soon as they started walking back home together.
“I know.” the blond said, the smirk never leaving his face as he allowed that other kid to praise him to high heavens and let himself bask in his praise despite keeping himself composed and haughty.
Katsuki enjoyed attention from everyone and anyone that would ever consider giving it to him, so he was particularly happy when a little group of kids from their same year but a different class caught up to them as they walked and congratulated him on his high scores.
“Yeah, it was whatever. Maths isn’t even that hard” he said with a shrug, knowing for a fact that it was hard and that many struggled, just not him.
“Hey, listen. We’re heading over to the arcade, wanna come?” Kazuo, the leader of that other little pack offered. It didn’t sound half bad, to be honest, and he knew he could definitely get away with bending the back home before 6 on school nights rule now that he had a sizable accomplishment to barter with under his belt.
“Sure, let’s go.” he offered with a nonchalant shrug, eliciting words of agreement from the other three kids in that little posey.
“We can’t, Kacchan.” Izuku pointed out, dutifully. “We need to go back to my house for dinner.”
“We can go for a little while, Deku” he countered.
“No we can’t! We need to go home.”
“Are you just going to obey your bitch?” Kazuo taunted, immediately prompting Katsuki to scowl.
He knew what the word meant. Kind of. He knew it was a bad word, and that it was used towards omegas or to imply someone was acting like an omega, but that was as far as his playground knowledge took him. It didn’t really matter, though, as whatever nuance was going over his head wasn’t needed for Katsuki to understand that he didn’t want people seeing Izuku as his omega and making fun of him for that because ew. He couldn’t let that stand.
“Of course not.” Katsuki said with a mean smirk on his lips before turning to face Izuku “I don’t even want to go with you, bitch. ”
Izuku’s lip wobbled right then, looking at Katsuki with big eyes hazy with tears as if giving him a few moments to recant his statement and make everything be okay again. He didn’t, doubling down on his current too cool for you position and walking off with Kazuo and his crew, leaving Izuku standing on his own and crying.
Katsuki would never admit it out loud, but he felt a tiny bit guilty once everything was said and done. It wasn’t rare at all to see Deku getting all teary eyed over one thing or another, but seeing the other kid just stand back looking defeated and sad didn’t sit too well with him.
He ended up apologising the next day, not so much because he felt like it (even though he kinda did ) but rather because his father was standing behind him with a frown on her face and hands on her hips, urging him on. It turned out that Izuku had cried a lot when he got home, which prompted Inko to call his parents and explain what had happened between both boys. Masaru and Mitsuki sat their son down and explained that wasn’t a nice word to use to describe anyone, much less to refer to someone as sweet and nice as Izuku because it had really hurt his feelings and that wasn't the right way to treat his friend. Despite rolling his eyes all through the lecture, Katsuki knew in his heart of hearts that his parents were right this one time.
Of course, Izuku had done nothing but accept the (mumbled and apparently reluctant) apology with a smile and a nod as the good natured kid he was and extend an invitation to go back up to his room to play All Might, Silver Age Street Crime: Super Brawl on his computer. And Katsuki could do nothing but nod and follow him just that once.