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Bakugo Katsuki with a younger sibling he’s so platonically head over heels with. Wants you to depend on him so much, and hates it when you rely on others. Typical platonic yandere sibling but the catch is that he has something to assist him in letting you solely depend on him only. That something? Your neurodevelopmental condition.
warning: micromanagement, minor domestic violence, ADHD; did research but again it might as well be inaccurate
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Katsuki was five when you were born, the loveliest thing that he had ever encountered in his life, aligning tiers with the memory when he had first received his quirk. You had bright, scarlet eyes, and your hair was a pretty shade of (h/c), of which father had explained you had inherited from your grandmother, his mom. You were a stark carbon copy of her.
But you were someone else in Katsuki’s eyes. He had cherished you so much the first time you stepped into the house you would come in terms to call home, but he wouldn’t admit it. He didn’t need to, anyway; Mitsuki already had countless photos to bind with time of Katsuki simply adoring everything you did as a baby. He happily fed you, was in charge of your baby backpack which consisted of your favorite toys and milk bottle, and overall took great care of you and acted like the responsible brother he was and would be in the following years to come - only a bit more of a despot.
Upon reaching toddler age, you showed signs of inheriting Masaru’s personality - timid, soft-spoken, and kind-hearted. You were the breather the Bakugou family needed, quite honestly. Whenever a yelling competition would start between your mother and older brother, you would get cranky and upset, and they didn’t want that. So the screaming would only ever happen during moments when you weren’t awake, because you were one hell of a deep sleeper, with your dad helping to drown out their obnoxious voices by playing classical music - something he liked.
While Katsuki adored you, you idolized him very much, doing various attempts to copy his attitude and tendencies though your kind heart and lack of quirk wouldn’t allow you to. Why wouldn’t you want to be like him? He was smart, awesome, and he got homework done right on time, too. In elementary, you’d often find yourself forgetting to do schoolwork, which resulted your grades to plummet down. If you did remember, you would avoid it for reasons unexplainable, even when you knew it was very important.
First signs of your condition.
He’d watch as Mitsuki would reprimand you for every mistake that could have been avoided, and you’d sit there, wondering to yourself why you’d done those mistakes even when they did indeed could have been avoided. In that way, you wouldn’t have been receiving verbal slaps from your hotheaded mother. After every reproach, she’d calm down and tell you that she was doing this (the yelling, the screeching, the disappointed staring) for your own good, so that you’d learn from your mistakes. You never did.
Katsuki would resent his mother for it, but also wondered the same: why were you so unreasonably irresponsible with yourself? He was around fourteen - you, nine - when he bothered to search the net of your possible condition; and there they were, all the telltales that you may actually have a little something called ADHD. He knew it wasn’t right to diagnose you with it yet it was so painfully obvious he probably didn’t even need a doctor to tell him there was something wrong with your pretty little head.
Despite that, he never made advances to suggest that you might be having some sort of mental condition, because then Mitsuki would consider psychiatry and you wouldn’t get to be so dependent on him as you were right now.
It’s less of a boost of his ego and more of the fuel of desire to want you to be entirely dependent on him. He loved it when you ask for his assistance regardless of how small the favor was; it made him feel aware of what you were doing and be in control of you. He liked it that way so he wouldn’t be so paranoid of you every single time.
It wasn’t like he was being unreasonable with fretting over you. You were kind and dumb - two traits that made you selfless to a fault. You’d do anything for the comfort of others it made you borderline suicidal - and due to that, due to not wanting to be of burden to others, you began forcing yourself to become independent, away from your brother’s constant watch. He didn’t like that. He wanted you to lean on him; he’d do anything for it.
Almost like he wanted you to be incapacitated just to get you to rely on him.
But it wasn’t like he’d actually act on the thought, right? It was just a thought. A stagnant one that he soon came to reconsider during his dorm life, when he only ever got to see you every few months. You’d call him every other day whenever you needed assistance with your homework. He’d call you every other day whenever he missed you - which was actually every other hour of the day.
Even far apart, you would still ask your brother for help.
“Alright, do the next number by yourself.” He stated one time in a phone call, when 11-year-old you had asked him to teach you improper fractions.
There was a timid ‘okay’ from your end, and then shuffling of pages, like you were referring to your notes to guide you with the equation. He answered three questions of his own homework whilst you solved. Five minutes in and he was starting to get impatient.
“Well?” He demanded.
“I-I um,” you staggered, “I don’t get it...”
“Which part?”
“Uh... everything...”
“Are you fucking kidding me?” He rhetorically asked, tone rough and aggravated. “Everything?”
He always cursed (and had inculcated into you that you were strictly prohibited from doing so), but this time particularly, it hurt. You knew you weren’t the smartest but he didn’t have to reprimand you for it. You couldn’t help yourself.
He reminded you of mom.
“I’m gonna teach you again, and you better get it right this time. Got it?” His tone was sharp, like the one Mitsuki had used on you back then. You held back a whimper. “So, first thing you gotta do is cross-multiply the-”
“Hey, I think I get it.” You hastily said, failing to cover the crack on your voice. “Thanks, oniichan.”
“Really?” He raised a brow. “Tell me the answer then.”
“You probably got a lot on your plate, huh? I bet hero studies is a lot.” You rambled. “I’m gonna go now. Thanks for tutoring me. Bye!”
“Hey wait-” but you ended the call before he could finish.
Shit. Right then he knew his words took a toll on you. He should have taken to account how sensitive you were. To be fair, you’d never acted that way whenever he would berate you for being so dumb. You’d just laugh it off and shrug with a timid smile. Wait, maybe you were just putting up a front and were actually ashamed of how you had to ask your brother for help every single time.
He called you several times after that but you didn’t pick up the phone. He called mom and demanded to give the phone to you but you told mom to tell him that you were busy studying.
Next day, homework was checked and you got a failing grade. Somehow, you weren’t disappointed. It was the first time you answered and finished schoolwork without the help of Katsuki.
Shiiit. He fucked up, he really did, and it was showing by how you weren’t so dependent on him anymore. Most times he was the one instigating the call and you now seldom did. It’d been weeks since you last asked him for help, but he still remembered, because he knew he had made you cry that time.
He returned home for the weekend, both excited and nervous to see you again because he thought you might have still harbored heavy feelings from that one phone call. Instead, you enthusiastically ran out the door and to your brother’s arms, eager to spend time with him after being far apart for his security as a hero student.
Good; you were ecstatic to see him as you were emotional the time he left for dormitory life. That meant he didn’t have to worry about your straying away from him anytime soon.
The both of you planned to finish a series in the duration of his time in the house. At one point, you said you were going to the restroom, but insisted he didn’t pause the episode for your sake. As you were out, his eyes scanned your room.
There was a thin stack of papers on the corner. Averting from the T.V., he took the papers and scanned them, soon coming to realize that they were your school works. All of which had barely passing grades.
When you returned, he ambled to you with an alarming look. He held out the papers to you. “What the fuck is this?”
You stammered, unpleasantly surprised. “W-what?”
“This!” He exclaimed, shoving them to you. “I don’t remember teaching you this shit. You did this all by yourself, huh? And you passed it without telling me?”
“W-well I-”
His pointer finger tapped harshly on your temple. “Why won’t you instill it into your goddamn brain?” He nearly growled. “Or is it that pea-sized you can’t even remember what I always tell you to do? You come to me when you find something difficult. You tell me when you don’t understand shit.”
There were tears in your eyes now, but this time he ignored them. He was focused on engraining into you what you should always do. Depend on him. “I just wanna do things without you for once...”
“So you’re gonna risk your grades for the sake of being independent?” He scoffed. “I’ll say this if it keeps you grounded, (y/n). There’s something fucking wrong with your brain. You’ll never be able to make it without me.”
god was it so tempting to actually... incapacitate you. Perhaps then you’d keep your hands to yourself and never again attempt to do something as dumb as that. Your feet might be worth the sacrifice; he’d carry you everywhere, know your location because all you’d have to do was sit and look pretty. Or maybe your hands. He’d feed you, get things for you, write for you and therefore know all your thoughts that you input in that journal of yours. Not that he’d never known of its content.
But it was just an idea. It wasn’t like he planned to do it. No; that would be too cruel.
Now he micromanages you. He knew of your schedule, your meals, hours spent on your phone and contact list. Being barely a teen, you weren’t too aware of his apparent possessiveness over you; all you thought was that you were only suffering the consequences of your own actions. Your own attempts of being independent.
Soon he was twenty when you were fifteen, still the loveliest thing he had ever encountered in his life - but not so lovely compared to when you were still submissive and knew no better. This time, you weren’t too timid to deviate against your brother’s wishes. His overprotectiveness you then thought was necessary and understandable was now irritating, superfluous, and a waste of both your time.
You were in your first year of high school and he was debuting as a rookie hero already rising in the ranks - still he was somehow able to find time to deal with you like you were some trite part of his routine. It irked you to the core. Who was he to micromanage your time like that? Did he really think you were incapable of fending for yourself that he just had to fit you into one of his chores? You felt insulted and, quite frankly, objectified.
And so you began deviating from his standards of you. Your curfew outside was 4:30PM but now you’d go home around 5. You weren’t allowed to touch your phone past 8:30PM but now you’d stay up until 11. He used to dictate your dress code, getting you dolled up in something way more conservative - so you’d wear [tank tops/spaghetti straps] just to piss him off. He wanted you to eat healthy? You spent your allowance on fast food for a week. Spend more time with him? You became busy in ‘group studies’ with your friends.
He’d let these not-so-little things slide at first, thinking that you were just in your phase of puberty. These come and go. But then he somehow knew that you had online friends and then your liberty was stripped off of you all of a sudden.
He had only ever wished to speak with you civilly about it, and you had hoped to return the same level of temperament, but then he proposed to confiscate your phone and from then on things got very heated.
What remaining good [boy/girl] exterior you had was forcibly ripped off your countenance as you yelled, voice cracking, “You never let me do the things I want! Leave me the fuck alone!”
His expression hardened upon hearing you cuss. “Don’t you fucking curse at me!”
“You’re a hypocrite!”
“And you’re a goddamn idiot! So fucking selfish!” He slammed his hand on the dining table, muscles from hero training prominent and terrifying. You flinched visibly. “So fucking selfish. Who are you to talk to me like that, ah? I’ve been watching you all my life I know what makes you happy, what makes you mad, what makes you cry! I made sure you were safe! Made sure you got your shit together with academics!”
“I never asked for that.” You replied, quivering.
“You never asked for that?” He reiterated, chuckling derisively. “I’m the reason you’re in UA’s general course right now. You wouldn’t have passed without me.”
You were so, so tired of arguing with your brother who’d done nothing but use insults for points in this argument. You were tearing up in frustration. “Why can’t you just let me be? What is wrong with you?”
“The reason why I’m like this,” he sneered, “is to accommodate with that tiny fucking rock in your skull you call a brain. You can barely survive on your own. god, no wonder mom gets mad at you a lot back then. Can’t use your brain for shit, fucking quirkless.”
It was like your world halted in motion. Regardless of anything, he never made an insult out of your lack of quirk. He knew it was a sensitive matter to you.
What made him stoop so low?
You glowered at him. “I hate you.”
“You might as well be dead without me.”
“Well I’d rather be dead than with you!” In the heat of the moment, you screeched. “My life would have been a lot better without you, anyway! I didn’t need some arrogant, egoistic bastard of a brother who gets off to micromanaging!”
You blinked and suddenly you were on the ground, white pressure on your cheek that you couldn’t distinguish until you looked at Katsuki’s outstretched hand and suddenly it was painful; you knew he slapped you so hard, and he knew what he’d just done.
He dragged you by the hair before you could scream, and you were forced on your legs to follow him as he went up the stairs and to a door. You were shoved into his room, locked, bruising on the face.
“Hey! What the hell?!” You shrieked, abruptly scrambling up and banging on the door. “Let me go!”
He didn’t answer. You heard footsteps getting farther and farther away, and then the shut of the front door echoed loudly across the house, which meant he went out for a breather.
You were hyperventilating. Vision blurry, breath heaving, head throbbing. There was something wet and warm trickling down the surface of your upper lip. Lifting your hand towards it, you came to realize that it wasn’t snot. You were bleeding from your nose.
You fell unconscious before you hit the ground.
===
There was something cold pressed against your cheek the moment you woke up, eyes squinted from the ceiling light above you. It felt soft and fabric-like, this something against your cheek, and then it was replaced with a hand so warm.
You looked to your side where Katsuki was, staring at you with a now collected countenance. You gasped, jolting from lying down on the bed and moving farther to the opposite of him.
“Hey, shh, it’s just me.” He consoled, voice completely mellow - quite the contrast to his usual self.
Your lips quivered, and tears surfaced on your bottom lids. The whimper on your throat came out when he made a move to join you on his bed (where you now rested) and shuffle near to your person. You shut your eyes when his hand - the dominant one that had hit you - came closer to you, only to hold your head and bring you onto him in an embrace.
You didn’t know what to do, when to move, so you just stilled in his hold, afraid and alert of every motion his body made.
He let go of you and looked at you in the eye. “Mom and dad are home.”
You struggled to remain the visual contact, blinking rapidly.
“When they ask you about your cheek, tell them that you got hit by a door, alright?”
Shitty excuse, but considering your tendencies, they’d most likely believe it.
When you took too long to answer, the hand behind your head squeezed tight. “Alright?”
“Y-yeah, yeah, alright.” You nodded urgently.
He may have not incapacitated you physically, but judging from your current disposition, Katsuki had a feeling that wouldn’t be needed. Not as long as you remain dependent and reliant on him.