The first time Katsuki met Izuku, they were five years old and a newborn respectively.
Literally a newborn.
Their mothers had been friends since their university times. The kinds of friends who stayed in touch, kept meeting up, met each other’s boyfriends and fiancés, went to each other’s weddings and, of course, met the newborn kids. They were the kind of friends who hoped their children could be the same kind of friends they were. So of course, Katsuki didn’t get to just wash his hands of Izuku and forget about him after that first meeting, no. He got to meet him regularly over the years, got to watch him grow from a diaper-shitting baby to a toddler.
And then Katsuki turned thirteen and was officially a teenager. With needs and wants demanding pocket money because like Hell would he keep asking his parents for literally everything. But of course, the old hag couldn’t just give it to him, no, that would be too easy. No, he had to fucking earn it.
That was how the babysitting gig originally started. Just a way to make some extra money. Katsuki didn’t enjoy it. (He didn’t, fuck off!) He was thirteen, a teenager, one of the cool kids with a cool Quirk who was going to be a hero. Izuku was eight, an annoying brat who only had All Might and games in his head and who dreamed of being a hero even though he had no Quirk and thus would never be one.
(Katsuki hadn’t been there when Izuku was diagnosed. He’d only seen him a few days later when their families got together for dinner again. It had been the first time he had seen Izuku quiet and meek instead of his usual, excited self. It had been a godsend. Katsuki had loved it and had hoped the nerd would stay quiet like this forever. Really, he had! And he hadn’t been relieved when the little boy had started smiling and chattering excitedly again after some time had passed. He hadn’t been!)
Katsuki didn’t enjoy the afternoon All Might games. He didn’t enjoy listening to Izuku prattle on about Quirks. He especially didn’t enjoy when the nerd chose to get hung up on his Quirk to the point of even making crude drawings of possible future hero costumes Katsuki could use. Of course, he didn’t keep the drawings, either, he only pretended to take them home so Izuku – or Deku as he’d started to call him by then – wouldn’t cry. He didn’t enjoy any of it. It was only a gig for some extra pocket money, nothing else.
So of course, when one day he didn’t have to pick Deku up from his elementary school because he’d gotten in trouble for getting into a fight and auntie Inko had been forced to pick him up early, the part of Katsuki that didn’t yearn for more pocket money was glad he didn’t have to deal with the little nerd. And of course, that same part of him was tremendously annoyed when he needed to go over to the Midoriyas in the afternoon to babysit anyway because auntie Inko needed to return to work.
“The Hell were you thinking picking a fight with a bunch of idiots twice your size?! Stupid Deku, of course they beat you up! You’re a fucking weakling twig, what did you expect?!” he yelled at the brat once auntie Inko was gone, but neither the volume nor the cursing seemed to matter much to the green-haired toddler. In fact, Deku merely pouted at him, his brows furrowed and tiny fists clenched at his sides with enough force that his entire arms were trembling.
“They were being mean to another boy, Kacchan! I can’t just look away from that!” Deku said emphatically, though he wouldn’t meet Katsuki’s eyes. “All Might wouldn’t,” he muttered next and it was those words more than anything else that gave Katsuki pause for all of five seconds before he scoffed and bonked Deku on the head.
“Ow! Kacchan!” the brat whined, holding both hands to his head. His lower lip was wobbling and his eyes were teary. Katsuki scowled. Another thing he hated about Deku: he was a fucking crybaby.
“All Might would have also known better than to get into a fight he couldn’t fucking win,” he reprimanded as he crouched in front of the brat to get a better look at his face. He had cuts and bruises all over him. Auntie Inko had obviously tried her best to clean up most of them, but some of the hits clearly must have been harder than anyone had thought because some of those bruises definitely needed some ice. “Get a fucking teacher next time instead of offering yourself as a replacement punching bag you idiot. You don’t even have a Quirk. What did you think you could do?”
“I…” Deku trailed off with a sniffle, bowing his head and raising a hand to rub at his eyes. Katsuki groaned and dropped his head into his hand, feeling exasperation rise within him. Here came the damn waterworks. “I just wanted to help…”
“Yeah, well, next time, don’t do it by getting yourself beat-up. That shit ain’t helping anyone, it just caused more trouble for auntie,” he said. His eyes narrowed and he half-glared at Deku, not that the boy noticed since his head was still bowed. The sniffling wasn’t stopping, either. He gave a tiny, weak nod, though.
“I’m sorry. I didn’t mean to cause trouble,” he said quietly. Katsuki clicked his tongue and looked away with a scowl, feeling something uncomfortable settle in his stomach.
“Whatever. I’m not the one you need to apologize to, brat.” Usually, Deku responded with something along the lines of ‘I’m not a brat’ or ‘that’s mean, Kacchan’ to the insult-nickname. But not this time. This time he only nodded again and rubbed at his eyes some more in a clear attempt to stop crying. Katsuki felt the uncomfortable feeling in his stomach coil tighter. He sighed and stood up, then grabbed one of Deku’s hands and pulled him along to the sofa in the living room. “Come on. Let me see if I can find some ice for those damn bruises and then we’ll watch an All Might movie or some shit.”
It didn’t happen from one second to the next like Katsuki hoped, but Deku did perk up during the course of the movie. By the time auntie Inko came home from work, he was all smiles and excitement again, if still slightly subdued compared to how energetic he could be. Katsuki considered it a success and a job well done, so his pocket money was well-earned.
Unfortunately, that wasn’t the last time Deku got into a fight of some sort. In fact, that had only been the first time. The times following that he clearly hadn’t been caught by the teachers because auntie Inko wasn’t called in again, but Katsuki could see the cuts and bruises when he came to pick him up. Needless to say, it led to more than one vicious scolding, which surprisingly enough, Deku just quietly accepted with his only reply only ever being ‘please don’t tell mom about this, please, Kacchan!’ sometimes even with a teary, pleading gaze to boot.
Katsuki didn’t tell auntie Inko, but it wasn’t because of Deku’s begging. Or rather, it was, just not in the way most people would assume. It wasn’t that he listened to the plea and agreed to do as asked. It was just that Deku’s behavior about the entire thing was just plain fucking weird and suspicious as all Hell and so Katsuki resolved to figure out what the fuck was actually going on before he told auntie Inko anything.
It took a bit of planning and maneuvering around time tables but eventually, Katsuki figured out a good way of booking it from his own school to Deku’s and then back again during lunch period. It meant he had a lot less time to actually eat lunch than he preferred, but he could handle it. Figuring what the fuck Deku was doing that ended up in him being always bruised was probably worth it. Probably. But Gods help him if it was something stupid, because then he was going to explode the little idiot, no questions asked.
Turned out it wasn’t something stupid. More… infuriating. And not actually Deku’s fault beyond the fact that the stupid nerd didn’t fucking say anything.
“Oi, the fuck do you shitheads think you’re doing?” Katsuki growled as his search made him follow loud jeering to the back of the school, where he found Deku and a few other boys and girls. It wouldn’t be an odd sight if they were playing but they obviously weren’t. Or at least it wasn’t a game that was pleasant for all involved because Deku was roughed up more than Katsuki’s ever seen him, had tear tracks on his face and was the only one sprawled in the dirt.
“K-K-Kacchan!” the nerd yelled in surprise before scrambling to his feet. “It’s… it’s not as bad as it looks! Really! I’m ok, see?”
“Shut it, Deku,” Katsuki snapped and the brat at least knew to listen because he closed his mouth with an audible click of his teeth before lowering his head and taking a step back. Katsuki barely noticed, he was too focused on the other little assholes standing in front of him. “I asked you a fucking question, damn shitheads,” he growled and the anger must have been more than obvious in his voice because the brats flinched away from him. Unsurprisingly, no one was really forthcoming with an answer. Which didn’t help Katsuki’s irritation at all. “Well? I’m waiting and I’m not fucking known for my patience. Spill already,” he growled, causing the brats to flinch again. One of them muttered something under their breath quietly, too quietly for Katsuki to hear. “Speak up so I can hear you, asshole!”
“I said we were only putting him in his place,” the brave girl finally said, squaring her shoulders and straightening her spine as she looked Katsuki straight in the eye. It would have been impressive if it hadn’t also been monumentally stupid because all her statement did was piss Katsuki off more.
“HAH?!” He wasn’t quite capable of articulating more than that and even if he had, he wouldn’t have bothered. Instead, he let his Quirk speak for him as his hands started to spark. Instead of scaring the children, however, it had the opposite effect as they stared in wonder, fear suddenly forgotten.
“Wow! Is that your Quirk? So cool!” the gushed over each other, as if they could salvage the situation by kissing his ass enough. “Not like that guy. Did you know he’s quirkless? But he still says he’ll be a hero! Everyone knows that ain’t possible! So of course we had to teach him… Uh…” the excited chatter pattered out as the kids actually looked at his face and realized that no, no amount of ass-kissing would actually save them. In fact, his expression made it so blatantly obvious that the little brats screamed in what could only be described as pure, unadulterated terror before running off.
“Get back here you little shitheads!” Katsuki yelled, fully prepared to run after them and give them a piece of his enraged mind. A very physical piece, mind you. It would be no less than they deserved. He was stopped, however, by the one child that hadn’t run away.
“Kacchan stop!” Deku called as he jumped forward and wrapped his tiny arms around one of Katsuki’s legs, clinging to his trousers with all his eight-year-old might. Understandably, that did nothing to actually physically stop Katsuki from charging after the little fuckers who more than deserved a beating. The teen stopped anyway and glared down at the little brat he babysat every now and again simply for the additional pocket money. “It’s ok. I’m ok.”
“Bullshit,” Katsuki spat, but he still crouched down and picked Deku up before walking towards the school gates, rather than following the little heathens wherever they’d run off to. Deku was quiet for a bit, but he started fidgeting the closer they got to the main gates.
“Kacchan, I should go back. I still have school,” he said quietly and fidgeted again, but didn’t make any real effort to get out of Katsuki’s arms. The blond, for his part, didn’t so much as slow down his gait. “And you still have school.”
“Fuck that,” the teen spat and readjusted his grip on the toddler so he could hold him more comfortably. “I’m taking you home.”
“But… but… you’ll get in trouble!”
“Don’t give a shit.”
“Kacchan!” Deku whined, honest to fucking God whined and buried his face in Katsuki’s neck. He started to sniffle again. “I don’t want Kacchan to get in trouble,” he sniffled. Katsuki sighed.
“Don’t worry about me, worry about yourself,” he muttered, although in all honesty, it was unlikely Deku would get into any sort of trouble himself. He was the victim here from what Katsuki could tell. “Also, I’m calling auntie Inko when we get back. I’m telling her everything and you’ll fucking tell her the names of each and every one of those assholes I saw with you. And any others that might not have been there today. Got it?”
His only reply was a meek nod and Deku wrapping his arms tightly around his neck in a somewhat awkward hug. The sniffling didn’t stop, either. In fact, it got worse, and Deku was shaking by the time they actually left the school. He didn’t outright sob, however, a thing Katsuki wasn’t sure whether he liked or not. On one hand, it spared him the noise of Deku’s bawling but on the other, knowing the brat was crying but for it to be so silent was fucking disturbing. For various reasons. Thankfully, Deku calmed down before they reached the Midoriya apartment, although there was no hiding the wet patch on Katsuki’s collar left by the nerd’s tears.
Of course, taking the nerd home meant he didn’t go back to school. Which meant his parents were called to inform them that he’d ditched. Which meant he did get into trouble and was adequately yelled at by the old hag. For all of five seconds before he managed to get a word in edgewise and fucking explain what actually happened.
Auntie Inko was understandably upset about the whole thing. Especially when Katsuki told her his suspicion on how long it’s been going on. Neither of them were prepared for what Deku had said when questioned on the matter of his silence, though.
“Izuku, honey, why didn’t you say anything? Why didn’t you come to me?” auntie Inko asked, hugging the kid close and crying into his hair much like he was once again crying into her chest. Katsuki looked away from the emotional scene uncomfortably.
“I didn’t want to cause mom any trouble,” came the barely-audible reply. Despite its quietness, though, Katsuki heard it loud and clear. In fact, he couldn’t have heard it any better if Deku had shouted it. He froze, eyes widening slightly at the reply as his own words from months earlier came back to him.
“Yeah, well, next time, don’t do it by getting yourself beat-up. That shit ain’t helping anyone, it just caused more trouble for auntie.”
Deku didn’t keep quiet because of what Katsuki had said, had he? He might be a little brat but he’s not that stupid… right?
Katsuki wasn’t at all reassured by the fact that he wasn’t exactly sure of that.
If the nerd had stayed quiet because of what Katsuki had said, then he’d definitely need to rectify it. Not now, though. Now he was just intruding on auntie Inko’s time with Deku. He needed to leave. So he did.
But he wasn’t going to let this slide. He wasn’t going to let Deku think it was ok for him to keep quiet about shit like that just because ‘he didn’t want to cause trouble for anybody’. Fuck that noise. If someone thought they could hurt Deku just because he was quirkless, they had another thing coming. First, Deku was going to learn to fucking speak up. Second, Katsuki was going to see to it he could stand up for himself, too. And third, he was going to make sure the nerd wouldn’t need to do either until he was old enough.
That meant he’d have to babysit more often. That wasn’t really an issue, though. In fact, quite the opposite, as more babysitting would mean more pocket money.
Although really, it very obviously wasn’t about the money anymore. In fact, it never really had been. Not that Katsuki was ever going to admit it to anyone.