𝕀𝕞𝕡𝕒𝕥𝕚𝕖𝕟𝕥 𝕐𝕖𝕝𝕝𝕠𝕨
ʚ pairing ɞ stepbrother!denki kaminari x reader
NSFW, dark content, aged up characters (21+)
ʚ word count ɞ 4.7k
ʚ summary ɞ having a step brother isn’t easy, especially if he is as fun and good looking as yours. you always got along just fine, but some very depraved and dark corner of your mind always forced you to look at him different, to imagine things that were taboo—to touch yourself while thinking of him. so when you had to crash at his place for a couple of days while your apartment was being fumigated, things escalated rather fast. i mean, it’s fine if it doesn’t go in, right?
ʚ tags ɞ mention of death (reader’s mother), tw stepcest, tw dubcon, masturbation, tw voyeurism, oral (f!receiving), tw spit, pussyjob, multiple orgasms, overstimulation, breeding, recording, blackmail
Most people say that having a parent remarry and having step-siblings is awful. You, however, don't see it that way.
Despite the devastation of losing your mother at a young age, you were grateful to your father for stepping up and taking care of you with everything he had after your mother's passing. You were 4 at the time, and things didn’t quite make sense until you got older—but with time, the more you matured, the more you came to terms with the situation. The older you got, the better you understood how much of a super dad you actually had—on the one hand, he always prioritized you, gave you everything he could and made sure that you didn’t miss out on anything, partially spoiling his little girl. On the other hand, he also chose to be very honest with you and talk to you about difficult topics instead of shying away from them. Therefore, you were able to understand what happened to your mother and were fully supported while working through the grief.
For all this, you were truly grateful to your dad, though, there came a time where you became aware of all the sacrifices that he had made for your sake as well. Turns out, that he avoided dating anyone else for the longest of times, resulting in you having to actually push him into pursuing romance and give him your slightly aggressive blessing.
"Dad, it's just a date." You roll your eyes at him.
"It feels like I'm betraying your mother, our family."
"Dad," you hold his gaze firmly. "Mom is gone. I'm in high school. And you deserve to be happy! Get out there, have some fun!" You push him forcefully out the front door and fix the collar of his shirt. "Don't be home too late, I’ll leave you some lasagna in the fridge. Now go!"
And when he found someone that made him happy, someone that made his worries go away, you were nothing but supportive. She was gorgeous and smart and had witty remarks that made you laugh, so you accepted her into your life. However, she also had a son, the same age as you—a tall and lanky boy named Denki Kaminari.
The first time you met him it was awkward, you were both 18—just about to graduate from high school, you were shy and quiet and he was just all over the place, bouncing with energy. But you found common ground, talking about games and anime, so you became friends rather quickly, progressively spending more and more time together. You’ve always been an honest person so denying that you thought he was handsome was pointless—fluffy blonde hair and amber eyes that turn gold in the sunlight, he had a very intoxicating smile, and most importantly of all—he made you laugh. But he was your dad’s girlfriend’s son, so he was—in all ways possible—off limits to you. Therefore you were content just admiring him from afar.
Sometimes, you stared a bit too much, making up scenarios in your head before bedtime, turning off all the lights before you push your panties aside, ashamed that it's him you’re thinking about.
And here you were, two years later walking your respective parents down the aisle, grinning at each other and testing out how it feels to refer to each other as brother and sister.
"Okay little sis, shall we hit the open bar, get wasted and embarrass our parents?"
"Totally, big brother," you winked at him and his face turned red at a comically fast pace.
"Okay, how about we drop the sis ‘n bro stuff? Feels weird."
"Does it now, big brother?" you bat your eyelashes at him, a seductive smile plastered on your lips. All Denki can manage is a dramatic groan in response, walking away quickly, hearing you cackle as the distance between you two grew larger.
He might be off limits, even more so now that he was your step brother, but you still enjoyed making him flustered. The perk of it was that it was extremely easy to do so—blow some air on his nape, trace a finger along his jawline and he’s ready to turn into a puddle on the floor.
And you did this within limits. Of course.
Your parents were happy that the both of you got along so well, and even happier when you both got accepted into the same college, living in the same city. Although you studied different courses, rarely seeing each other on campus, you did occasionally go to parties together, Denki making sure to get your drunk ass back home safely every time. He was kind and dependent and always had your back.
Even more so when you had discovered that your suspiciously cheap rental apartment was infested with termites, having to be fully fumigated, and you had to ask your step brother if you could crash at his place for a couple of days.
“Of course!” his voice sounded chipper over the phone. “We’re so totally having a Marvel marathon, I am not taking no for an answer, pack your shit and come over, I’ll have nachos ready in 30 minutes.”
The line went silent as he hung up and you found yourself smiling at his enthusiasm. A voice at the back of your head told you he’d be such a fine boyfriend—if he wasn’t your step brother.
Yet, you allowed yourself a few minutes of imagining what kind of dates he would take you on—arcade dates, bringing you to museums so he can narrate over the audio guide with absolute nonsense and making some lame joke about van Gogh and George Weasly and ‘hole-y’. You shake your head as if to purge the thoughts and you get on with packing your essentials for the next couple of days.
You stare at your underwear drawer and contemplate. Would it be weird if you pick the sexiest lingerie you own... just to stay at your step brother's place for a few days? Totally not.
“Self-care.” You say to yourself as you take out several lacy thongs and bralettes that match, carefully placing them in your suitcase. You just like wearing nice underwear, what’s the big deal? It’s only for you to see anyway.
Right?
Happy with the items you’ve packed, double checking if you’ve got your toothbrush and all your chargers— you take a deep breath and vacate your apartment, heading over to Denki’s.
“We should’ve just gotten an apartment together, it would’ve been so much cheaper and nicer.” Denki whined as he helped you carry your suitcase up the stairs, as his building had no elevator.
“So what I’m hearing is you want to see my pretty face every day, correct?” you smirked, noticing the barely visible butt clench he did upon hearing your words, at which you chuckled. “Honestly, you’d get sick of me in about a week so be glad we don’t live together.”
He grumbles something you can't understand under his breath and you allow him to move on from the topic.
The first night in his apartment goes well—you have dinner together and then proceed with a quiet movie night. Snuggled together under a fuzzy blanket, the light of the TV was illuminating Denki’s face, showing off his best features—playful amber eyes, devilish smile and a sharp jawline. You spent more time looking at said face and judging the softness of his blonde locks, rather than looking at whatever movie he put on for you.
The realization that you haven’t gotten laid for a few months now and that your step brother is awfully handsome makes you feel a certain way, insides knotting up and devious thoughts plaguing your mind.
Mindlessly, you place your hand on his thigh under the blanket and you feel his body immediately tense up under your touch. Kaminari tries to play it off cool, like nothing has happened, keeping his gaze fixed on the screen.
So that’s how you wanna play, hm?
Your hand travels up and down his thigh, caressing it, squeezing it every once in a while and slowly but surely going further up with each stroke. At the same time you maintain a blank façade, pretending to be fully focused on the movie.
Once your hand starts getting dangerously close to his now semi-hard cock, Denki lets out a fake cough and gets up under the pretense of getting ice cream and some new drinks. Your eyes follow his frame as he exits the room almost skittishly and the dangerous thoughts make you lick your lips in excitement.
He’d look very cute broken and torn up over experiencing sexual desire towards his little step sister.
A plan begins forming in your head.
You spend the rest of the evening making Denki’s temperature rise and his ears turn red with embarrassment—a subtle press of your tits against his arm when you cling to it, removing stray hairs from his face with a gentle hand, accidentally tracing his jawline with your finger, keeping his gaze just a tad longer than appropriate.
Meanwhile, Kaminari continues shifting uncomfortably in his seat, trying to find a pose that would allow him to hide how turned on he is, purposefully avoiding looking down your cleavage or observing how your shorts were riding up your thighs, revealing more plush skin that he wanted to sink his teeth into.
You don’t push too far though, you still had a couple of more days staying at his place, plenty of time to make your plan come to fruition. The movie comes to an end and you both decide to call it a night—you kiss his cheek and thank him again for allowing you to stay over, wishing him a good night and heading over to the guest bedroom where you were staying. His own room was right next door and you begin wondering how thin the walls really are.
Removing your clothes and kicking your panties aside, you make yourself comfortable on the bed and slide your hands down your torso, imagining how much bigger Denki’s would be, warmer than your own, eager.
Your mind conjures images of your step brother losing himself under you as you hover over his face, tongue lapping at your core like a starved man, staring up at you with those intoxicating cat-like amber eyes. Cupping your breast, a low moan escapes your lips as your other hand glides between your legs, humming with approval of how wet you are because of your step brother.
You touch yourself, rolling your nipples between your thumb and index finger, drawing circles on your clit and letting your mind relish in all the taboo things you want to do with Denki, paying less and less attention to the needy sounds bouncing off of the walls, yet hoping that they reach Denki’s ears.
And they do—in the other room Denki has his ear pressed to the wall, already fumbling with the zipper of his pants, his face so red and hot because he knows how wrong this is. You’re his little sister, not by blood, but you were family, and God, you were still incredibly gorgeous and just his type.
He had put so much effort over the years into not being a creep, not watching your ass as you walk away or blatantly staring at your tits. He had learned to be subtle, to be unnoticeable, to steal glances and satisfy himself by just imagining your lips around his cock—just that, nothing more.
But now, having you in his apartment, being surrounded by the scent of your perfume mixed with the coconut-scented shampoo you use—he was losing his mind. You’d been so much more touchy than usual this evening and your hand on his thigh made him feel dirty, so here he was now, listening in on you, knowing full well what you were doing and how incredibly wrong this was, invading your privacy and taking advantage of it, but he couldn’t help it.
Lip tucked between his teeth to keep quiet, he spits onto his palm and spreads his saliva over his cock, slowly fucking into his fist, trying to match your pace he was trying to guess from the cute whines he could hear. He imagined you spreading your pussy for him, beckoning him to take advantage of you, calling him ‘big brother’ in that seductive voice of yours that could drive him mad. Hearing you panting louder, breath uneven and needy, he allows himself to go faster, now picturing himself pushing his cock into your tight little hole, imagining his cum leaking out of you and just like that, faster than he’s ever experienced, he came in his hand shooting thick ropes of cum onto his knuckles and pillow, his heart threatening to leave his chest cavity.
The post-nut clarity hits him and Denki is plagued with shame and guilt, quickly removing his pillowcase and bedsheets and tossing them to the side, replacing the old one with new clean ones while mentally berating himself, feeling disgusted with his own actions.
He no longer hears you moaning in the other room, the sweet sound dying down and feels relieved, shoving his face into the freshly changed pillow and trying not to scream at himself. It felt like he had committed a crime, a sin of some sort, his own guilty conscience not allowing him to get much sleep, forcing Kaminari to toss and turn for the most part of the night, shaking his head as if trying to push away the thoughts of your breasts in his mouth out of his mind by force.
The next day, he seems to be the same, shoulders sagged with guilt, barely managing to look you in the eye during breakfast. Both of you had classes, so you drive to campus together and Denki, happy to have a distraction from his lewd thoughts about his own step sister.
You on the other hand keep your focus on your plan the entire day, not paying attention to a single lecture, forgetting to even eat lunch—completely consumed by your desire to have your step brother snap.
You had it all figured out—with your classes finishing earlier than Kaminari’s, you could head home before him and use the spare key he gave you to prepare for his return. You knew your brother was very curious, not a doubt in your mind that he would seek you out when he got in and you hoped that what he found would be enough to make Denki lose control.
And to no surprise, everything goes exactly according to your vision. You shower and put on some of that pretty lingerie you had brought with you, leaving the door to your room slightly cracked open, whilst entertaining yourself until the target audience for your little performance had returned home.
You’re lying on the bed—face down, ass up when you hear the front door open, the sound making you quiver with excitement, heart beating even faster as his footsteps approach, the fingers playing with your clit speeding up, your arousal dribbling down your thighs in fat droplets
The house was suspiciously quiet, leading Denki to believe you hadn’t gotten back yet. He’d kicked his shoes off to the side, tossing his bag onto the couch before heading towards his room with the intention to shed off his outside clothes and switch into something more comfortable. That didn’t end up being the case. Noticing that the door to your room was ajar, he takes a quick glance through the crack, freezing in his tracks as his sunshine eyes fixate on your drooling cunt, clenching around nothing, your arousal soaked fingers toying with your puffy folds. In this position you can’t see him, so Kaminari basks in the sight for a few moments to enjoy this, to memorize it and engrave the image of your cute cunt into his mind—trying hard to ignore the raging boner in his pants.
Kaminari gulps, feeling as if there’s a massive lump in his throat, right hand absentmindedly adjusting his now hard cock.
“Denks,” your needy voice shocks him out of his trance. “Please...”
His brain short circuits.
Time feels frozen, the noise of the outside world fading into nothing and the sound of his heartbeat ringing in his head deafeningly loud.
His name just left your mouth.
You said his name. You begged for him.
Once more, Kaminari hears his name, watching you arch your back even more, spreading your legs further and sinking down onto the bed while begging for him incoherently.
Denki sits there, motionless, watching his little step sister cumming hard, making a mess on the bed sheets while chanting his name.
For many years, his sanity and patience were tested—like a string tightly pulled back. In this single moment as he watched his step sister shake in the aftermath of her orgasm, that string finally snapped.
He opens the door, slowly at first and then in two short strides he’s behind you, pulling you up by the hair, pressing your back to his chest and breathing hard down your neck.
“You’re a fucking tease, you know that little sis?” Inhaling in your scent, the blonde holds you tight against him, tugging on your hair again to force you to look up at the ceiling—knowing he wouldn’t be able to have any self-restraint if he looked into your eyes.
“Moaning my name as you cum? You want your big brother that badly, hm?” His throbbing shaft presses against your ass, still clad in jeans, but you could feel it through the fabric.
You shut your eyes in embarrassment but don’t attempt to escape his grip, the lack of response to his question makes Denki even more impatient.
“Answer.” he growls in your ear.
“Y-Yes,” your voice comes out uneven. “I w-want my stepbrother, please.”
Your eyes stay tightly shut but your body gives your reaction away—shaking with anticipation and excitement, feeling your juices begin to slide between your folds again.
“Didn’t think you were this sick in the head, but who am I to refuse my precious little sister, huh?” You can't see his face but you can hear the sinister smile, feel how thrilled he is by the way his grip on you tightens. Suddenly, Kaminari’s pushing your head back down onto the mattress, crouching down to take a good look at your glistening wet cunt. Your little pleasure nub looks so cute and swollen he can't help himself by giving it an experimental lick, appreciating the way your body tenses. So he does it again and again—paying good attention to your needy bud, kissing and lightly sucking on it, mapping out how you react to each movement.
You drip like sweet honey onto Denki’s tongue, showering him in lustful mewls and needy grinds against his face, tiny fists balling the sheets when he slips his tongue inside your needy hole. He eats you out like a man starving, holding your hips steadily in place. Your big brother loves the way your thighs tremble and your breath is uneven and he is determined to get you to cum on his tongue, he needs it.
And it doesn’t take long for your slick to overflow from your body, the thought alone that your step brother’s chin was shining with your mess was enough to make you melt into a puddle, the taboo aspect of what you were doing pushing you over the edge too quickly.
With a silent cry, you cum hard, pressing yourself against Kaminari’s face, a trickle of drool sliding down your own chin as your eyes roll back from pleasure so intense, your senses become overloaded for a moment that all you see is white.
Before you come back down from your high and your soul returns to its body, Denki has managed to kick aside his jeans and boxers, knees digging into the edge of the mattress and his leaking cock glides between your sticky folds.
For a split second an uneasy feeling captures your heart in an icy grip.
“Don’t worry. It’s okay if it doesn’t go in, right little sis?” the blonde’s voice is thickly coated with smugness, with a sense of toxicity that should be so incredibly off-putting, yet it makes your insides twist with desire.
Two orgasms in, and your head starts to feel fuzzy, the heat emanating from his length rubbing against your slit making you feel like you have one foot off of the edge of insanity. You circle your ass against his dick, desperate and teary-eyed, pleading and chanting his name like it’s a prayer, enjoying the friction of your step brother’s mushroom cockhead against your sensitive clit.
His hands explore the expanse of your body, following the curves and dips of your hips, squeezing the doughy skin on your hips. Denki was greedily taking in every weak sigh you let out and every shudder you respond with, basking in the knowledge that he’s the one making his little sister drip down on his girth, oozing into the sheets and making a mess of them. You feel the heat rising inside you, knots forming in the pit of your stomach, the madness creeping further across your brain with the sound of Denki’s filthy words in your ear. The sound of his dick slipping back and forth on your wet cunt. Everything is so obscene, even the scent of him is working you up more, the knots twisting tighter.
You crave more.
You shouldn’t.
Denki—he’s your step brother there would be so many consequences, so many drawbacks of your current situation.
But consequences be damned, because the vein on the underside of his shaft feels so good against your sensitive clit, so much so that your brain throws all logic and reason out the window.
Denki is nearly as desperate as you are, and he gripes and grunts loudly—so close to release, just from the wetness of your pretty pussy engulfing him. So when you lift your hips up and angle them against the head of his girth, pushing past your entrance with ease—he nearly loses it.
The softness and warmth of your cunt wrapping around his cock makes him feel like his soul is ascending to high heavens, eyes rolling back in his skull and body shaking in ecstasy with every inch of him that you take until he’s fully sheathed in you, balls laying flat against your swollen pleasure nub.
You don’t give him time to prepare, to react even—slamming your hips back against his as quickly as your body can handle, yearning for that the feeling of the tip of his dick reaching deep inside of you and helping the pressure build even faster.
Cock drunk and cross-eyed, absolutely debauched and unashamed, your body forces out another orgasm, causing your muscles to spasm with a string of curses leaving your pretty lips as your soft walls clamp down on the blonde’s dick.
Denki sees stars, the only thought crossing his mind in that moment being that he will never have pussy this good ever again—so snug against him, pulsing violently around his length, selfishly sucking him in deeper. And with that singular thought, your step brother decides to fuck you stupid, make you feel the exact same way he does—like nothing would ever be good enough again.
Snapping out of the trance your perfect pussy has put him in, he props up a leg on the bed, pulling his length out of your heat and marveling at the way your cunt gleams luxuriously with the crude mix of his precum and your erotic juices, clenching and spasming around nothing. You whimper, but before you can clearly state your protest, Kaminari spits on your raw and abused mound, slamming his entire length into you once more, with only a single motion, setting a meteoric pace—spreading your ass cheeks apart so he can fuck into you harder.
Forgetting all his previous misgivings about fucking his little sister, Denki gives into his carnal desire and takes everything he can from you. A thumb now collecting the arousal from between your legs and using it as lubrication to toy with your pert ass, slowly pushing in the digit into you as you become impossibly tighter around him.
“One more time—I need to feel you cum around my cock one more time, sis,” Angling his hips to hit your sweet spot with every thrust, Denki practically makes you scream out his name, the blistering heat of his cockhead kissing your cervix repeatedly, leaving your brain absolutely scrambled.
You don’t even think it’s possible for you to cum again, but the telltale signs of your impending orgasm are there. However, it feels different this time, as if there’s some sort of pressure bubbling up inside you—like a volcano ready to erupt. A string of pleas leave your wet lips, not really knowing what you’re begging for but Denki understands—maintaining the same angle and rhythm, he sneaks a hand around your torso to rub gentle circles over your puffy clit, the action pushing you over the edge.
With a loud cry, you tense up around him so hard that he has to pull out, clear liquid gushing from your aching cunt as you squirt onto the bed and taint Kaminari’s golden skin, body shaking violently with tears streaming down your face until you’re overwhelmed by the feeling. The view of your pussy gushing and squirting is so enticing, but Denki is too greedy to allow you time to calm down, grabbing your hips and propping you up, lining his tip with your sopping entrance again and drilling into you at a ravenous pace.
You’re too sensitive, too sore, even—but he holds you firm against his chest, a hand around your throat, slightly restricting your breathing and keeping you from protesting while the blonde chases down his own release.
“ ‘m not fucking pulling out,” he growls into the shell of your ear, a cruel smile twitching at the corners of his lips. Kaminari’s words make you clamp down greedily on him, body instinctively trying to milk him for all he’s worth.
A couple more ruthless thrusts of his cock deep into your abused little pussy and he’s thrown over the edge, balls tightening and thick cum spilling deep into your womb—there’s so much of it, too much, to the point where it’s leaking out of your hole before he’s even pulled out. Your insides are burning hot with his seed and you can’t even be bothered to remind yourself if you’re on birth control or not, too fucked out to be able to conjure up a coherent thought.
Slowly pulling away, the tall blonde stares at your pink puffy pussy, thick cum oozing out in globs and dripping down your thighs—he collects the sticky substance with two fingers and promptly pushes the digits past your soft lips.
“Nasty little step sister, if I had known you were this slutty and desperate, I wouldn’t have spent countless nights fucking my fist—I would’ve fucked this pretty pussy of yours instead.” He taps the two digits that were in your mouth against your clit and your body jolts.
He moves away from the bed, grabbing something from your desk that you can’t see, still trying to collect yourself. Before you even had the chance to ask what it was, your step brother shows you his phone, the screen showing you a replay of what had just happened minutes before—a video of Denki fucking into you with no sound.
“Y-You recorded that?” the panic sobers you up as you quickly rise from the bed and try to take the phone from him.
But Kaminari’s much faster.
“Of course.” The corners of his lips turn upwards but the smile doesn’t quite reach his eyes. His body language shifts as he leans down, eyes raking over your naked, soiled body, a cool and foreboding aura seeping into the room, sneaking up on you. “Leverage, step sis.”
The words feel icy, goosebumps rising on your skin—with you barely recognizing the amber eyes looking down at you.
It was twisted, it was wrong, but one way or another—Denki Kaminari will keep you all to himself.
𝐃𝐈𝐒𝐂𝐋𝐀𝐈𝐌𝐄𝐑! I do not own any of the characters or people mentioned in my work. these are works of pure fiction that do not reflect the views, opinions, or actions of any person, real or fictional. Furthermore, all characters I write for [thirsts, drabbles, fics, etc.] are aged up to 21 or older – they are adults with adult characteristics presented and written in adult contexts.
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