Just do what I say (Senku x reader) (nsfw)
Warnings: smut, commanding Senku, jealous Senku, blow job
“Hey, don’t drop that.” A harsh child like voice snapped at you, making you grip the model rocket harder as you packed it back inside of Senkus room. You were young, and yet your friend dragged you around to test rockets. Rockets! He was incredibly intelligent, and yet you were both so young. It made your childhood crush on him grow stronger, fueled by the fascination for science and boys. It was truly a deadly combination at the time.
“But it’s heavy.” You whined, tiny arms struggling to carry such heavy things around for him. Usually you would have Taiju helping you, but in rare occasions like today it was just the two of you. Which completely left you alone to carry all the heavy items, being the stronger one.
“Just get it to my room.” Senku led you further down through his home, guiding you back to where his room was even as you stumbled. He didn’t even move to help catch you or wait, just let out exasperated sighs each time you fumbled. Finally, you couldn’t right yourself as you tripped over your own feet. You tried your best to not fall on the rocket, and so you leaned backwards and fell straight on your back, letting everything smack you in the face. “Hey! I said not to drop it!”
A loud burst of crying interrupted his annoyance, filling the home with your cries of pain from underneath the heavy project. Loud footsteps came running from behind you, carried by parental urgency. Soon, from underneath the model rocket you were freed by strong hands, that quickly scooped you up into their arms.
“Senku! What have I told you about using your friends like this?” Byakuya, lovely Byakuya. Even now with his anger focused downward, you stared up at him like he was your saving grace. And he was yelling at Senku in your honor, how amazing! “Come on, we have a first aid kit in the kitchen.”
Soon you were whisked away to the kitchen, and delicately put on the kitchen counter as he rummaged around for the bandaids. Now that you were not being carried you could tell you had blood running down your forehead. Mostly likely from getting hit in the face with metal scraps. Your childlike eyes watched the man in front of you, not with love but with admiration. Forget your childish crush on Senku, you wanted to find someone like his father. A genuine man.
And with that new discovery, you realized your friendship with Senku was heavily based on your crush. Now that the illusion was shattered, you did want to get back at him for always using you as free labor. Once his dad had fixed you up and deposited you back in Senkus room, you looked at the other white haired boy.
“Senku, I’ve decided I’m going to marry your father.”
Even then, Senku was offended by the idea.
Years and years passed after that interaction, your friendship with him quickly diminished after you realized you were being used. Yeah, you confessed that you had been interested in him, but clearly loved his dad more now. Senku waved you off, not caring beyond being a little disgusted in your attraction to his father.
Throughout middle school, anytime you seen his dad you would fangirl over him. Mostly just to annoy Senku. As you got older it had turned from disgust and annoyance to frustration. He much preferred your focus to be on him, complimenting him and his work rather than his father. At some point he got fed up and told you the honest truth, that you couldn’t marry his dad and to grow up. Maybe he was jealous, maybe he was grossed out. Either way he had snapped at you and hurt your feelings.
“You’re just too rough with people Senku, you don’t know how to treat a lady.” The offhanded comment was easily brushed off by the white haired boy, who didn’t care.
“If you’re calling yourself a lady, I have more news for you.”
Then just as you were about to go to high school with everyone, you moved schools and never seen him again. Now that you were a full fledged adult and in college, that interaction long ago was barely a funny story to tell your friends.
And that was only a rare occurrence, because who in college really talked about their childhood? Especially when they were swamped with classes and trying to find the nearest distraction from the stress. You drifted through friend groups about as much as everyone did, casting a wide net and having a lot of friends but few close ones.
Maybe that’s how you found out so many people from your grade school went to the same college as you. It started with running into Taiju in the halls, and nearly being crushed in a giant hug. It then was followed by the crafts club trying to kidnap recruit you after they seen you were taking an advanced art class. That’s how you ran into another childhood friend, of course.
Even with both of those encounters, your long lost childhood crush wasn’t exactly on your mind. You didn’t even really have an idea of what he looked like now, so maybe if you seen him you wouldn’t recognize him at all.
That was your thought process’s right up until you literally ran into him in the halls, foreheads smacking against each other and both of you falling down. Books, papers, pens and everything else a student could need cascaded around you as you rubbed your eyes.
“Sorry about that.” And then you heard him, Ishigami Senku. His voice was different, but that tone was unmistakable. He gathered up both his and your fallen stuff, before holding out a hand to you. As you reached up and took it, your shock wore off a little.
“Oh wow,” crimson eyes bore into yours, a joint recognition crossing between you as you both remembered. A smirk tugged at the corner of his lips, reminding you so much of the flutter your heart used to get from him. “You look like your dad.”
“Thanks I-“ pausing, the smirk wiped clean of his face and he squinted at you.
‘Senku, I’m going to marry your dad.’
“Are you still on about that?” Clearly, both parties remembered what had followed your childhood crush on him. Senku more than ever felt annoyed by the words, especially now that he was an adult and the idea of someone fucking his dad was way grosser. Especially you.
“He is a good looking man, that’s all I’m saying. Ah, I better get to class.” You snatched your books out of his hands, crushing his personal space. As soon as you got close you could feel the heat radiating from him, and hearing the slight ‘tsk’ he made at you.
“How am I supposed to take that?” His words fell over you, making you laugh at his clear annoyance. Maybe it wasn’t so bad you ran into him, now the story had a really funny conclusion.
“See ya!” And with that, you left.
Without even explaining what it meant, really meant, that he looked like his father.
It seemed life had a weird obsession with pushing you and Senku together after that, because suddenly you were running into each other. Suddenly friend groups you had joined also included him, group study sessions were randomly tutored by Senku, and even as you tried to become friends again with Yuzuriha you found Senku was still as close as ever with her.
And so, you decided to tease him.
“Wow Senku, with your hair up like that you look like your dad!”
“Yeah he’s smart but did you know he’s the son of an astronaut?”
“I haven’t seen Byakuya in a while, how is he?”
And every single thing pushed Senku further and further into a fit. That was a terrible way to describe an adult, but that was the best wording for what was happening to him. You’d become insufferable within the weeks since he’d ran into you again. Every time he seen you, he was reminded that you were somehow in love with his dad.
He also was trying his best to not come across as “rough”.
The words you had said to him years ago still lingered in his mind, now more prevalent than ever. Any time he was around you it was like walking a tight rope. He wanted to tell you to be quiet and stop talking, but didn’t want to prove you right. Even if it was something you had said long ago. Just being near you had him on edge, and yet he still felt an urge to get close to you again.
Maybe he was feeling nostalgic for the days of your youth, maybe it was something else.
It was that exact reason he suggested Yuzuriha invite you out with the larger friend group. There was talks of going bar hopping that weekend, and he hoped that somehow this would be an easier way to reconnect. He didn’t worry about getting drunk and acting a fool, that was everyone else’s job. He would just wait til the right moment came up and try to mend your old bonds.
It would be alright, as long as everything went according to plan.
So of course, when that night rolled around and everyone was out at the first bar, a few shots in everyone including Senku, everything went wrong.
“Wait, you’ve never met his dad?” A bright grin was spread across your face, the joy of your newfound joke reignited. Gen, Chrome, and Kohaku were sitting at a table with you. Small glasses littered the table, along with random foods to go along with them. You were a giggling mess already, though not quite drunk. You pulled out your phone and scrolled through social media, desperately searching for a photo of Byakuya.
“Ah! Here we go.” You flipped the phone around to show the group the photo of Senkus father in his astronaut suit, smiling and so excited for his trip. “This is the kindest, sweetest man.”
“And you said he’s Senkus father? What happened in that gene pool?” Gen zoomed in on the photo, taking in the sweet face he seen. “Our little Senku could charm his way out of a bag.”
“I’m adopted, which you know.” Senkus hand shot out and stole your phone away from you, his other hand tilting your head up to look at him, “and I am charming and sweet too, which you know as well.”
“For as long as I’ve known you, you’ve never been either of those things to me.” Your eyes slid sideways to look at your phone, still in his hands. You felt like your point was proven already.
“Wait, how long have you guys know each other? I thought you just met?” Kohaku seemed to not be the only one at the table who was confused. Especially with how easily Senku had grabbed you and your things.
“Since we were kids. Some people used to have the biggest crush on me.” Now it was Senkus turn to tease you. Yes, he still wanted to make amends, but when the opportunity for revenge comes up, well…
“I did not! I liked your dad!” You had no shame in saying that, you’d made it obvious so far. Your cheeks were flushing anyway, showing that maybe there was truth to what he was saying.
“Oh? I recall you used to follow me around like a little puppy. Always telling me how smart and cool I was. You even confessed to me once.” Senkus hand was still placed on your chin, keeping your eyes on him as he stood above you from behind. Your head fell back against his lower abdomen as you let out a tiny huff, clearly annoyed you couldn’t deny it. “That’s what I thought.”
“This is why I find it hard to believe anyone would like you man, you’re so… what’s the word for this?” Chrome waved at the two of you, your eyes flicking up to Senkus and meeting them. There was something there that told you not to say what you were thinking, daring you not to do it.
“Rough. That’s the word you’re looking for.” As soon as you said it something behind his eyes snapped, though only you saw. Suddenly your jokes and the teasing all seemed a little too dangerous to keep up with. “Ah, Senku I didn’t mean-“
“No, I get it.” His hand let go of you at the same time he placed your phone back on the table. “I’m gonna go see what Tsukasa is up to. Have fun staring at pictures of an old man.” And with that, he walked off. Though something told you that you weren’t done talking to him that night.
Since the plan was to bar hop, that’s exactly what the group did. You jumped around from group to group, never settling too long since you wanted to socialize with everyone. You liked having a lot of friends, and this was definitely a large friend group. At the second bar you sat with Yuzuriha and a white haired guy name Ukyo. More shots were poured and drank, locking in your now tipsy state. Occasionally you felt eyes on you, and it made you shiver.
You knew who it was, and felt worried about what you had done. The realization that you would have to deal with Senku at some point made you switch your drink of choice to water.
The conversation in the group drifted off to crafting and good headphones, nothing more serious than that. You started to feel more sober than you had all night, just in time for your impending doom.
“We need to talk.” Senkus voice dragged you away from the conversation you were in, and even as you cast pleading looks at your friends you got nothing. So, you stood up and followed him outside.
Once outside the building the noise level died down dramatically, and a cool wind nipped at your skin through your clothes. You pulled your arms together and tried to keep warm as you avoided his gaze.
“I’m sorry, I think I’ve pushed the jokes too far haven’t I?” Senku didn’t respond to your words, just stared at you with that same look in his eyes. It flustered you, considering how talkative he usually was. “I won’t mention your dad anymore, and I am sorry about saying you’re too rough.”
Again, nothing. You shifted uncomfortably on your toes, trying to figure out what you needed to say to him.
Senku was in his head, debating over his next course of actions. He could just forgive and forget, apologize for being harsh and rekindle your friendship.
Senku stepped forward, getting into your space until you were up against the wall of the bar. His breath mingled with yours, warm in the chilly air. For such a friendly guy, he could be a little scary when he wanted to be.
“How can you say I’m too rough when you’ve never even seen me like that?” He didn’t touch you, didn’t yell. You would’ve expected yelling, maybe some giant fight. Instead you got this. His red eyes bore into you, making you feel bare and awkward.
“Like what?” You finally met his eyes again, and felt a fluttering in your stomach. What had he been saying earlier about your childhood crush? It seemed to be making its way back to the surface. He had grown up to be a very handsome man. No one could deny that. You’d teased him about it before, but you found yourself attracted to him, and not because of his father.
“You know what I mean. You just won’t say it.” He was so close to you, so in your space. One of his hands moved to grab you by the hips and close any distance that were left. “You always sucked at following orders.”
“You just had unrealistic expectations, we were kids.” Was it just the unexpected closeness, or did his hand on you make you feel things. Things like an imposing sense of ownership over you and charged emotions. You couldn’t look away from him now, stuck staring up at him. His hair was neatly tied back, perfect for keeping it out of his face. Even still two pieces fell forward and ruined the otherwise perfect style.
“We aren’t kids any more, though you’re still behaving like one.” Both of you were close to breaking. Both wondering who was going to make a move, whether it be screaming or something else. Senku, who was so angry at you, maybe himself, and feeling oddly annoyed that you denied liking him long ago. Or would it be you? You certainly were feeling far more flustered than you ever had before. Even if you could be mad at him for dragging you out here just to insult you, your sudden attraction to him was clouding your mind.
Suddenly you both closed the gap between you, lips connecting in a desperate attempt to break the tension. His hand tightened on you, making you groan into his dominating kiss. It was hot, messy, and completely different than how either of you had interacted thus far. You had even been aware Senku could have such a needy, passionate side to him. Not until his lips were on you again and again, short breaks to grasp at air before pushing back again. He needed you, anyone who caught the exchange could see that. You could feel it in his fingers digging into your skin, and his lips trailing down your neck, only to be followed by a harsh bite.
As soon as his teeth left your shoulder, leaving imprints behind that wouldn’t fade any time soon, the door to the bar opened. You both backed away from each other, the moment ruined. You tugged your shirt to cover the fresh mark and averted your eyes from his.
“Hey, that’s where you two went. Did you uh… talk it out?” Yuzuriha tried to keep her voice calm, unsure of what kind of ‘talk’ you’d been having out here. You could tell from her body language that she expected an argument and was relieved to have caught the moment after.
“Yeah, everything’s great.” Senkus dry laugh hit you as he walked past you, and back into the bar. Your mutual friend shot you a look, and since you were stunned, all you could offer her was a shrug.
“Let’s just go check out the ideas for the next bar.”
“So uh, what’s been going on between you and that new girl Yuzirha brought?” It had been a week since the bar trip, and Chrome had just now seemingly worked up the nerve to ask Senku about you. Not that Senku had seen you during that week, too swamped with classes to do much else.
The question still had a weighted answer, regardless. What was going on between you? Or rather, what had happened. He went from wanting to reconnect, to so mad he couldn’t think straight, to making out with you. If he hadn’t been there for it all he wouldn’t believe it was true.
The heated moment between you both had made some feelings Senku had been pushing down finally break into the open. He liked you, a lot. Now that he had kissed you, he could even admit that he had liked you back as kids. His childhood crush on you had went undiscovered and unrecognized of course. He hadn’t ever really thought about how he sought out your company, your compliments, your voice. Young him didn’t have the capacity to think about anything other than science. He still struggled daily to focus on anything other than his passion and his school work.
Now there was you. Back in his life and yet still too far away. It was like the time after you moved away all over again. Back then he had found himself looking for you even after knowing you weren’t going to be there anymore. He went on with high school and never really connected with people the way he had with you. He’d barely made new friends in college and that was only because they didn’t let him get away.
“Hey, Senku.” Chrome snapped a finger in front of his face, and senkus attention was pulled back to the present. Right, he was at school, sitting at a table with Chrome and Gen. He shook his head and gave them a shrug, not knowing what they wanted to hear from him.
“We were friends as kids, what about it?” The looks on their faces told him they were not buying what he was selling.
“Yeah I don’t think childhood friends act like that.” Gen then stood up and mimicked what he had done to you. Gen’s lifted chromes face up from behind and did his best impression. “I’m charming and sweet, aren’t I?”
“Oh Senku, you’re so rough with me.” Chrome did high pitched and horrible impression of you, and batted his eyes at Gen.
“I know you’re in love with me, just say it.” Gen still impersonated Senku, though the words he said were absolutely nothing like the man.
“No no, I couldn’t!” Chrome threw a hand up over his eyes and then burst out laughing. The mockery was clearly over, both friends cackling with their joke. Senku gripped the table, a twitch suddenly appearing in his eye as he let them act out their little show.
“I didn’t know you were both blind as well as stupid, how tragic that must be to live like that.” Deep breaths, in and out. He calmed himself down and waved them both off. “We all know it didn’t go like that so why embellish?”
“Well it may not have been exact, but the idea is the same. I’ve never seen you act like that with someone Senku, something must be going on.” Gen sat back down, no longer pretending to be Senku. Though Senku suspected that particular impression would make a return some day.
“How about next time someone fangirls over your parents and we see how you react.”
“Well, maybe you just need to show her that the newer model is more fun!” Ryusui’s loud voice rang out as he abruptly entered the conversation, a hearty laugh following his words. “Who would want an older model?”
“Thanks, I love being compared to cars. Next you’ll tell me I need to go on a test drive.” At his words, Senku watched Ryusui’s mouth snapped shut. He had perfectly called the next suggestions his friend had.
“Well you better, because I just heard that this guy in my class wants to bang her. You’ve got competition.” Ryusui patted him on the back, a sympathetic look in his eyes. As if he’d already lost the race he didn’t even know about. Nor had he entered.
“I’m going to go before you all lower my IQ anymore.” And with that, Senku got up from the table just in time to hear Gen and Chrome reenacting the bar interaction for Ryusui.
And so Senku went off to find you.
Finding someone was both a nightmare, and relatively easy. He figured out where your dorm was within a few minutes, but waiting until you’d be alone was another task. Eventually, he seen your roommate walk out of your dorm and he quickly made his way inside. It wasn’t weird that he just wanted to be alone when he spoke to you, right? After your last interaction it seemed like the best bet.
He made his way up the stairs and down the hallway, before stopping in front of your door. What was he there to do exactly? Confess or tell you he had made a mistake? His knuckles hit the hard wood of your door a few times. He was still undecided about what he was going to do when you opened the door.
There you stood, in a cozy outfit perfect for a long night of studying. You felt embarrassed once you seen Senku, realizing you were definitely underdressed to be opening a door to the hallway. Just shorts and a tshirt with nothing in under it, that was all.
It was apparently exactly what Senku needed to make his decision. He stepped into your room without and invite and closed the door behind him, trapping you against it.
“Hey Senku, what are you doing here?” Your voice was calm, even if you didn’t feel that way. Your heart was pounding in your chest at the sight of him.
“Figured if you were going to call me rough and tell me I didn’t know how to treat a lady, I’d show you in person.”
And then you were against the door, slammed into it by his body pressing against yours in all the right ways. His pupils were wide, taking in the sight of you so flustered and shocked at his declaration. You had your bottom lip caught between your teeth, clearly trying to hide any reactions.
“How do you propose to do that?” Your hands felt limp and useless, even as his connected with your body and gripped yours tight. That look was back, the same one as before.
“You’re going to do what I say, when I say it. It’s time you learned how to properly follow orders. First up, kiss me.” You blinked, and then blinked again. Had he just said all of that to you? His hand at your hip squeezed hard, urging you to do what he said. So you did.
Your lips connected with his in the same hunger they had the first time. With you pinned like this, Senku had perfect control of you as he dominated you. Each kiss was hotter than the last, each marking that you had done as you were told to.
Eventually Senku pulled you away from the door and moved over to your small dorm room bed. His lips were puffy from kissing you like that, and the look in his eyes were determined.
“On your knees.” The command was said with a firm tone, indicating there wasn’t an option to argue. You sunk down onto your knees, the hard wood underneath sure to bruise them the next day. Senku undid his pants, the sound of a zipper so close to your face making the heat rise even faster to your cheeks. He pulled himself free of his pants and positioned his length perfectly lined up with your mouth. You had a feeling you knew what he was going to ask of you next.
“Suck.” Your mouth was already watering by the time he spoke again. Your lips parted around the reddening tip, slowly taking him into your mouth. He wasn’t fully hard yet, but it still was a hard mouthful to take. Your tongue lapped at every inch of him, feeling the weight grow and fill your mouth further than you thought possible. One of his hands came down to cup your cheek, guiding you up and down on him. Tears started to prick at your eyes each time he sunk you down on him again. But you didn’t stop, not when he hadn’t told you to yet.
“Wow, you can listen.” His laugh cut through the sounds of you gagging on him. You flicked your eyes up to look at him, just in time to see his smirk spread over his lips. The tip hit the back of your throat, causing a loud moan to vibrate over his length. As soon as he heard that, he stilled himself there. You were struggling to breathe with your mouth so full, but he wasn’t letting you move.
“Wish I could take a picture of this, you look good down there.” The words were demeaning and harsh, exactly something you wouldn’t have expected of him. Finally he pulled you off of him and let you cough and breathe again. His hand gently pushed away any hair that had fallen into your face. How could he be so tender and so controlling at once?
“On the bed, take your shorts off.” His hands worked to removed his shirt, followed by the rest of his clothes. You did as you were told and stood up, leaving your shorts on the floor as you did. You gently placed yourself on the edge of the bed, until a look from him told you that you had gotten the last part wrong. You inched your way higher up on the bed, your eyes following his hands as he dropped his underwear and left himself bare in front of you.
“Face down.” He amended his previous statement and waited for you to move. You rolled over onto your stomach and pushed your face in the sheets. You could feel as the bed dipped behind you with his weight. Then his rough hands slid up the backs of yours thighs, making you instinctively raise your thighs up to meet his hands. “Eager much?”
You muttered a response but it was drowned out in the covers. Not that he bothered to listen anyway as he raised you up to meet his hips. He wished he trusted his time constraints to be generous enough to allow him to prep you better. Relying just on your arousal from sucking his dick wasn’t the best, but at least you’d gotten him wet enough. He pushed the tip inside of you, stretching you out around him and taking in the muffled groans you let out. He briefly considered letting you adjust, but the long forgotten words came back to him again.
He shoved fully inside of you, letting his length stretch you further until he was finally inside of you fully. Even with such little prep, you were already so wet. His eyes fell closed as he took it in, the way you wrapped so tight around him. He dragged himself back out half way, before sinning back down into you. You were a loud mess under him, just like he expected you to be.
“Use your words.” He hissed out the command as his hips slammed back in and out, in and out of you. It was maddening how good you felt around him and he felt himself getting lost in the feeling.
“Senku— please I—“ you were choking on your tears from the sensations he caused you, but you didn’t ask him to stop. Instead when your words failed you, you used your hand to guide his length in and out of you. At first he didn’t get it, but as you started to guide him out and back in faster he figured it out.
“Faster? Is that it?” He pushed your hand away and held it down into the bed, but did listen to your request. His thrusts picked up speed, the growing wetness on him aiding the efforts. Soon enough your thighs were dripping with fluids and his length was soaking. Another laugh broke out of his throat as he grabbed your ass and used it to guide you along him. Each thrust was heaven, each moan you let out music to his ears.
“So, still think I’m too rough? Maybe you wanna call for a sweet and caring man?” A rough slap cracked across your cheek leaving a red mark in its wake. He’d probably never fuck you like this again, or at least not without good reason. Though he did plan to fuck you again. This wasn’t a once off thing. “Answer me.”
“No! No I don’t want anyone else, Only you Senku-“ a cry erupted from your throat and you hurried your head in the covers again. Each thrust hit the deepest part of you. You could feel himself getting lost bruising you on the inside. Everything about this was a claim, a way to mark you as his. His and only his.
You definitely weren’t thinking about his dad, that much was obvious to everyone.
“Good, cause we have exactly 37 minutes left before your roommate gets back.”
I am starting to get sad about how little interaction/ likes I get on posts now compared to before I went on a break. I don’t mean this as a pity party but it is just slightly disheartening to see. I hope this fic does better, I’ve been much more excited to write this one
