Work Text:
Katsuki never says the word vampire, for a few reasons.
One, it’s fucking stupid. Also, it’s not fucking accurate. He can go out in the sun, he has a reflection, he can eat fucking garlic. He can do literally everything he was able to do before he got bit by some weirdo when he was ten, it’s just that now he has to do all of it while sucking on a bag of blood like a fucking juicebox.
But it’s fine. He adapts. He can still be the number one hero, he just needs to occasionally duck in a back alley and suck down a rat. It’d take more than that to keep him down.
Still, he doesn’t tell anyone, just his parents and the doctor who told them that whatever quirk the asshole who had bit a child had, it had permanently altered the makeup of Katsuki’s DNA, but only in one specific way: his body needed blood to survive.
Katsuki, ten years old and a douchebag and trying to pretend he wasn’t freaking out about what was going on, had said “everybody needs blood to survive.”
The doctor had given him a look. He had a horrible bedside manner and weird glasses. Katsuki hated him fiercely. “You need to drink it,” he said bluntly. Katsuki thought he might vomit, and that made him angrier, but he was also really scared, and that made him really angry—
“Does it have to be… human blood?” He’d never heard his mother’s voice so small and timid. It only made him angrier.
“No, although that’ll probably taste better.” The doctor sits back and crosses his legs. “We’ve had a few cases of this around the country. So far no one has gone,” he spins his finger around near his temple, indicating he meant crazy, “but refusing to drink the blood your body needs will cause you to go insane with thirst and eventually die, same as if you refused to eat.”
“Can I still eat?”
The doctor shrugged. “If you really want to, I guess. It won’t give your body what it needs to stay alive, but it’ll still taste good.”
“Are there really no other options?” Now his mother’s voice sounded more like what he was used to, too loud in the hospital room, too severe, but protective. “There is no way to cure this? To revert it? Have the police discovered anything about the pervert going around infecting children with some kind of vampiric infection, or are we just supposed to get some kind of frequent flier miles for the goddamn blood bank?”
“We don’t have a lot of information yet. We’ve never seen anything like this. Quirks are evolving faster than we can keep up.”
“What kind of a useless damn quirk does this, anyway?” His mother didn’t even yell at him for swearing.
The doctor shrugged. “Not all quirks are particularly useful.”
“So… this is it?” His father asked, and his usual calm voice has an undercurrent of emotion running through it that Katsuki had never heard before. “There’s nothing else to do? We just have to… live like this?”
“Well,” the doctor said. “He has to live like this,” nodding at Katsuki.
Sparks burst from his palms. He wasn’t going to cry. He wasn’t going to cry. Heroes didn’t cry—
The first time he bites Deku, they’re twelve and he has the stupid nerd shoved up against the brick wall at the back of the school. Everyone else has gone home for the day, but Katsuki’s hanging around because he feels like shit. He’s so fucking hungry. It had been a few days since he’d fed, because he hates eating animals and the bagged blood his mother brings home from the hospital, courtesy of that stupid doctor, tastes like shit. It tastes stale. He fucking hates it, just like he hates the fact that he has to drink blood in the first place, and he hates the fucking fangs that keep trying to poke out of his mouth whenever he gets really hungry, and he hates stupid fucking Deku and how he always pities Katsuki, as if Deku had any right, the useless quirkless fuck, it should have been Deku who’d got hit with this quirk—
“K-Kacchan?” His voice is high pitched and whiny and so goddamn annoying. Katsuki can smell his fear, and it makes his mouth water.
No, really. He boxes Deku in with his arms and he smirks at him and he leans in to take some of the anger and fear battling around inside him out on the useless nerd, but as soon as he gets close he stops and stares at Deku with wide eyes.
He smells so fucking good.
Katsuki occasionally gets the urge to bite the people around him, especially when he’s hungry, but it’s never been anything he can’t handle. It isn’t like the books or legends make it, some insatiable urge that he can’t fight, an animal instinct that overrides his higher functioning and makes him want only one thing, consequences be damned.
Or at least, it wasn’t until right now.
Has he really not gotten this close to Deku in two years? Or is it just that he hasn’t fed in a few days? No one else had ever smelled like this, though, even if he was hungry. He’d never had this reaction with any of his friends. The fangs in his mouth extend, and his palms are smoking.
He needs to fucking bite Deku.
“K-Kacchan?!” Deku squeaks. “W-what are you doing?” He says this because Katsuki leans forward and shoves his nose in Deku’s neck, inhaling deeply. His palm explodes against the brick and Deku flinches, but Katsuki doesn’t let him get away.
“Hey, Deku,” he says, leaning back and grinning at Deku, enjoying the way Deku’s eyes focused on the fangs in his mouth, growing wide in fear. He pushes himself further against the wall, as if it will give way and he’ll be able to escape. Fat chance. “How’d you like to be useful for once in your pathetic life?”
Deku doesn’t get a chance to answer, because Katsuki bites down on his fucking neck.
His fangs break easily through Deku’s skin, and the immediate bliss and relief he feels is like nothing he’s ever experienced. Deku cries out in pain and jerks, but Katsuki is stronger and bigger than him and can make explosions in his palms and has his teeth sunk in Deku’s stupid neck and there’s nowhere he can go. His hands push uselessly at Katsuki’s chest, and Katsuki grabs them and pins them against the wall and keeps drinking.
He can’t stop. It’s like nothing he’s ever had before. In the early days, before they’d figured it all out, his parents would let him bite them and feed when he needed to, and although that had definitely tasted better than the bagged blood, it had been nowhere near this. Like sunshine bursting on his fucking tongue. He closes his eyes and he gets lost in the scent and the taste, and he almost doesn’t notice when Deku’s wrists go limp and his knees give out.
With more self-control than Katsuki had frankly thought he was capable of, he pulls away. Deku’s head lolls on his neck, and Katsuki feels panic flutter to life in his chest. If he killed the stupid nerd, his entire future is going to be ruined. He moves away so Deku slumps to the ground, and Katsuki crouches in front of him and lifts his head by the hair, fingers trying to locate the pulse on his neck, ignoring the puncture marks and the blood that wells up there and how much he wants to put his fucking mouth back on it and drain Deku dry.
He finds the nerd’s pulse, faint but there. Katsuki shakes him a bit and smacks him on the face.
“C’mon, shitty Deku,” he says. “You better not ruin my fucking future because you’re a pathetic wimp who can’t even handle a little blood loss.” He’s really pale. Katsuki feels a growing pressure in his chest, the panic getting worse.
“Deku,” he hisses, hitting him again, and after a moment Deku’s eyelids flutter and he moans.
“K…chan…”
He’s alive. Katsuki stands up and runs.
He spends the next eighteen hours freaking the fuck out. He holes up in his room and ignores his parents and waits for the knock on the door from— the police, or the school, or Midoriya Inko, or anyone. Someone to come take him away for what he did. For biting without permission. For almost killing someone. Even if it was useless Deku.
The knock on the door never comes; Katsuki eventually falls into a restless sleep, and he isn’t even able to enjoy how sated and full he feels. The next morning he wakes up for school, and he still hasn’t been arrested, and his dad asks if he’s feeling better and his mom asks if he’s done being a whiny hermit, and they don’t know anything.
Okay, so Deku didn’t tell any adults or authorities. But there’s no way he wasn’t going to tell their shitty classmates. This was perfect revenge for the nerd, the ability to get back at Katsuki, to ruin him. He was going to get to school and everyone was going to know and they were going to laugh at him and—
It didn’t matter, he didn’t have any options. He had to go to class; running and hiding would be way fucking worse. He marches into the classroom with his head high and his shoulders braced for whatever was going to meet him.
Which is:
Nothing. The idiots he lets hang around him grin and wave in greeting, and Katsuki’s eyes flick around the classroom, landing on Deku’s seat. He sees hunched shoulders, Deku’s collar buttoned high and hiding his neck. Katsuki waits. Maybe he was going to announce the secret live in front of the class now that Katsuki is here.
But Deku stays quiet. The teacher orders him to sit down and he does, and he goes through the whole day waiting for Deku to do it, to tell everyone, to ruin everything, and he never fucking does.
It makes Katsuki really fucking angry.
The goddamn nerd must be looking down on him, pitying him. How dare he? Did he feel sorry for Katsuki and was keeping his secret, or was he planning to use it to blackmail him? Or was he just going to wait, keep Katsuki stressed out and tense, never knowing when the truth was going to come out?
Not if Katsuki fucking kills him first.
When school ends that day Deku flies out of his seat and out of the classroom, and Katsuki almost vaults a desk in his haste to follow him. No way was the useless asshole getting away from him. Katsuki wanted goddamn answers, and Deku was going to give them to him.
“Get the fuck back here, Deku,” he shouts down the hall at Deku’s retreating back. People give them both a wide berth, well used to Katsuki’s temper and well aware of what will happen if they try to interfere. Katsuki throws himself down the hallway and manages to wrap his fingers around Deku’s scrawny arm before he can get out the front door.
“No you fucking don’t, nerd,” he growls, hauling Deku down the hallway and away from prying eyes. Deku lets out a fearful squeak.
“K-Kacchan! W-what—”
Katsuki throws him in the supply closet next to the gym and shuts the door behind them, glowering down at Deku, who shrinks against the wall and stares up at Katsuki with wide, scared eyes, like Katsuki was a predator and he was the prey.
He guesses they kind of are. Deku’s sweet scent surrounds him in the small closet, and it makes his mouth water and his fangs poke out.
“Why didn’t you tell anyone?” He hisses, voice quiet but deadly. Deku winces.
“I-I—”
“What? Too stupid to speak now, too?”
Something determined flashes in Deku’s gaze, but it’s gone as Deku slumps against the wall. “I… well it’s a secret, right? You probably don’t want people to know?”
Katsuki’s lip curls. Who knew the shit nerd had it in him?
“Is that what this is? Blackmail? The fuck do you want from me, Deku?”
“N-no!” Deku’s eyes widen and he waves his hands around. “No, that’s not what it is! I s-swear! I just— Kacchan wants to be a hero! And you… this…”
And this— this is way fucking worse than if Deku had been blackmailing him. Katsuki would have preferred that to this. This kindness. Because now Deku has Katsuki’s entire future in the palm of his hands and in the puncture marks on his neck, and at any time he could ruin everything Katsuki is working towards, and he’s not going to because he’s nice and—
He’s protecting Katsuki. Useless, quirkless, shitty Deku, never knew when to stop, when he wasn’t welcome. Sticking his goddamn nose in where it didn’t belong. And now Katsuki owes him. The thought makes him sick. Deku was beneath him, and now Katsuki owed him a debt?
He slams his hand on the wall beside Deku’s head, satisfied at the way he flinches. “If you tell a fucking soul, Deku, I will drain you dry. Understand?”
Deku squeaks and nods. “I p-promise I won’t tell, Kacchan.”
Katsuki is so fucking angry. He needs to get out of this closet before he actually does murder Deku. He kicks the door open and turns back one more time to glower back at Deku’s shaking form.
“Not a word, shithead, or you’ll regret it.”
And Deku never breathes a word of it to anybody.
And Deku tells him he’s going to go to UA, too. Deku stands up to him.
And Deku jumps him in to save him from that fucking slime bastard.
And Deku— Deku has a fucking quirk. That he’s been hiding, and for what? To make Katsuki feel weak? Is that why the nerd thought he was so much better, because of his hidden quirk, because of Katsuki’s fangs? Had he been holding onto Katsuki’s secret for three years just to let it out at the worst possible time?
Was Deku going to take UA away from him? Is that why he hadn’t told anyone yet? He was waiting for the time it would hurt the most?
(And through it all, through it all he has to deal with the memory of how good Deku had tasted, like nothing he’d ever had before.)
Once again, Katsuki goes through the days waiting for someone to show up at his door and take his dreams away. But they get through the exam, and Deku doesn’t say anything, and Katsuki gets a letter welcoming him to UA, and Deku doesn’t say anything, and Katsuki goes to class and sits in front of the useless fucking nerd…
and he still doesn’t say anything.
“I got my quirk from someone else.”
Katsuki turns around. Deku’s arm is in a sling and he looks like shit, but he stares Katsuki in the eyes in a way he never used to be able to.
“I can’t say from who but… it’s borrowed power, and it’s still kind of useless to me, but I-I wasn’t tricking you, or pretending I didn’t have a quirk when I did. I just, I needed to let you know. And one day I’m going to make this borrowed power my own, and beat you with it for real!”
Katsuki narrows his eyes. What the fuck was he talking about, borrowed power? Quirks couldn’t be passed onto someone else, could they?
“A-and also…” Deku looks around and then takes a step closer, voice lowering. “We’re even now, see? With… with secrets. I have one of yours, and now you have one of mine.”
Katsuki’s hands are shaking. He clenches them into fists and tries to will them to stop and he can’t, because he’s so angry and upset and scared, because for his whole fucking life he’s been the best and now he’s here and that fucking Half n Half bastard had been so strong, and now here was fucking Deku, and Katsuki is going to be left behind. He swipes an arm across his eyes, the fact that he was tearing up only serving to make him angrier.
“From here on, I’m gonna beat you all,” he growls at Deku. “Enjoy your win, shitty nerd, because it’ll never happen again.”
The second time he bites Deku is after Kamino. After their fight. He’s barely eaten since he got back, because every time he tries he feels like he’s going to be sick, and the bit of blood he’d managed to get down had tasted awful, so— he hasn’t really eaten. Before he goes to meet Deku he forces down some blood, knowing he’d need it, but it’s just enough to get him to win, and he can’t really eat after that.
The second night of their house arrest, Deku knocks on Katsuki’s door around midnight. He wakes up, because he was really only half asleep, anyway, because he’s been sleeping like shit since he got back. He eyes Deku warily before he moves aside to let him in Katsuki’s bedroom, to say whatever the hell it is he wants. He’s insistent he’s never looked down on Katsuki, and he’d love to believe that, but he can’t come up with any other reason why Deku would be here, at midnight, unless it was to rub something in.
Deku stands in the middle of the room, crosses his arms, stands up straight, and looks directly at Katsuki. He’s gotten so much more confident lately, while Katsuki feels like he’s shrinking away. “When was the last time you ate?”
This question slogs it’s way through Katsuki’s brain. “What?”
“The last time you ate,” Deku says, and then he fucking turns around and looks around Katsuki’s room, taking note of the mini fridge in the corner. He stalks over to it.
“Deku, fuck off—”
He opens the fridge; it’s almost completely full. When Deku turns back to Katsuki, there’s anger in his eyes, and Katsuki thinks, is this it? Are they finally going to have this conversation? Is Deku finally going to tear into Katsuki the way he deserves to? He’s not sure why it took so long, or why it’s now, but whatever. It’s not like he doesn’t deserve it.
“You haven’t been eating since you got back from Kamino, have you?” Deku says lowly, fury in his words. Katsuki doesn’t answer him, because he doesn’t want to, and because just because he deserves whatever Deku dishes out doesn’t mean he has to make it easier.
“I noticed you were off, but I didn’t really put it together until we fought. You weren’t as powerful.”
“Still beat you,” Katsuki spits out, because the way Deku is talking and looking at him kind of feels like he’s being flayed alive.
“Yes,” Deku concedes. “I have a long way to go before I’ll be able to beat you, but when I pass you I want it to be because I earned it, not because you’re being a moron who won’t eat.”
Katsuki jerks back and looks at Deku in surprise. His words burn as they settle inside Katsuki’s head, because he’s right. How is he supposed to be the number one hero, surpass All Might’s legacy, if he’s not at full strength? But still—
“I’m trying,” he says, and it comes out a little more hoarsely than he’d have liked. He crosses to his desk and kicks his chair out, sitting down and rubbing his hands over his face. “Everything tastes like shit and I—” I fucking hate that I’m like this.
“So what? You’re just drinking enough to make sure you don’t go crazy?”
Katsuki looks at him sharply. “How do you know—”
Deku actually rolls his eyes at him. Katsuki feels like he’s in a parallel universe. “It’s me, Kacchan. You don’t think I went home and immediately started researching?”
“I figured you’d have gone home and told the fucking police.”
Deku blinks at him. “Well, I didn’t,” he says, stupidly. “I’ve been researching. I keep researching. They still haven’t found the person who does this, but there’s been a few more cases in the past few years. And they’re doing research into some of the people who’ve been infected by the quirk to see if they can understand it better—”
Yeah, he knows, because they’d asked him and he’d told them in no uncertain terms to fuck off before he blasted them to bits.
“But the point is,” Deku says seriously, “That you can’t keep doing this. Never mind that you can’t be a strong hero if you’re weak from hunger, you’ll barely be able to be a person. I— this is basically like an eating disorder, Kacchan, and I can’t just let you starve yourself!”
Katsuki closes his eyes and tries to breathe through the anger welling up inside him. He tries to take a step back and think about what Deku’s saying in the context of what he knows now, that he’s not looking down on Katsuki, that he’s just— good and kind and worried, even though Katsuki is the last person Deku should ever be concerned about.
“Fuck, okay, I’ll fucking— I’ll deal with it, okay? I’ll start drinking more, just get out of my fucking room.”
“You said everything tastes like shit,” Deku points out. Katsuki grits his teeth and groans in frustration.
“ Ugh, Deku, what the fuck do you want me to do, then?”
He meant it rhetorically, but Deku says, simply and seemingly seriously, “I want you to bite me.”
Katsuki looks up so fast he almost strains his fucking neck. Deku looks back at him. Katsuki waits for— something. Something else. For Deku to say or do anything else because what he just said made no fucking sense.
“What?”
“Fresh human blood tastes the best,” Deku says, and hearing the easy, nonchalant way he just says that makes Katsuki feel dizzy. Deku should have been disgusted by him, not standing in the middle of his bedroom at midnight giving Katsuki some kind of fucked up intervention about how he needs to start drinking blood again. “That’s what everyone says, and that makes the most sense, anyway. It’ll make you stronger and it’ll help you get back to normal so you can start managing yourself in whatever way you did before.”
“I’m not going to bite you,” Katsuki says through gritted teeth.
“Why not?” Deku asks, because he’s ridiculous and has no sense of self-preservation what so fucking ever.
“Because I’m not,” Katsuki says again, leaning back in his chair and covering his face with his hands.
“Kacchan, you need to get your strength back up—”
“I’m not doing that again!” He shouts, sitting up and yelling at stupid Deku and his stupid face and the words Katsuki doesn’t want him to be saying, because he wants to bite him so fucking badly. “I’m not— they thought I’d make a good villain and maybe I would have back then, but I’m not fucking doing that to anyone again.”
Deku’s face softens, and Katsuki hates that. It’s not pity, he has to remind himself. It’s not pity, it’s not pity, Deku’s just that stupid and soft. “You won’t be,” he says, and he takes a few steps closer to where Katsuki is sitting down. “Because I’m offering. There’s a huge difference between taking something by force and taking something that’s being freely offered.” Taking something by force. Katsuki thinks of Deku’s limp wrists in his hands against the wall of their school and feels nauseous.
“You shouldn’t be offering,” Katsuki says, ignoring how close Deku’s gotten, ignoring how good he smells. His fangs, which he’s been just barely in control of since he got back, are out in full force and are not going away. “You shouldn’t want to be near me. I almost killed you.”
“You didn’t,” Deku says. “And frankly, if you were going to kill me it would have been back then. But you stopped even then, Kacchan.” He steps even closer, so Katsuki’s knees are brushing up against his stupid thick thighs. “You’re not a villain because of this, Kacchan,” he says, and Katsuki hates how much he needs to hear those words. “Someone hurt you when you were a kid and now you’re trying to deal with it, and that doesn’t make you bad.”
“The way I dealt with it is what makes me bad,” he says, because he’s too weak and hungry and all of his energy is going towards not pinning Deku to the ground and sinking his teeth into him, which means he doesn’t have as much energy to guard his heart and stop those weaknesses and vulnerabilities from escaping.
“Kacchan,” Deku says, his voice still soft and calming. “I’m not trying to… diminish what happened, because it was— it was scary and dangerous and it could have ended a lot worse than it did and it really fucked me up, if I’m being honest—” guilt spikes through Katsuki, but Deku keeps going. “But it was also a few years ago, and we’re both really different people. And you never did it again.”
“Stop giving me so much credit.”
“I’m not trying to give you credit,” Deku says, and he sounds annoyed. “I’m trying to get you to bite me.”
“What is wrong with you?” Katsuki hisses. He doesn’t like that he has to look up at Deku from this angle. “Are you stupid or do you really just not care about what happens to you?”
“Kacchan, we can either do this the easy way or the hard way.”
“The fuck is that supposed to mean? You think you can—”
Deku plants himself down so he’s straddling Katsuki’s lap, grabs him by the hair, and shoves his face in Deku’s neck. And Katsuki may be strong, but he’s not this fucking strong. He moans as his mouth makes contact with Deku’s neck, skin salty beneath his tongue, and Deku shivers as Katsuki’s fangs brush up against his skin, and then he gasps and grips Katsuki’s shoulders as he bites down and breaks the skin.
It’s better than he remembered. He moans again as the taste floods his senses, and one of his hands comes up to grab Deku’s wild hair and angle his head more. Deku mumbles something that might have been Katsuki’s name, but he’s lost to anything except the taste on his tongue and the scent in his nose and the way his entire body rejoices as he finally gives it what it’s been craving since the first time he’d lost control and sunk his teeth into Deku. No bagged blood could ever stand up to this. Nothing has ever tasted this good.
“Kacchan,” Deku says again, and his hand slips past the collar of Katsuki’s shirt to dig into his bare shoulders. “Too much—”
He pulls away. He’s not sure if he’ll be able to until he does, and even then he dives back in to lick at the wound on Deku’s neck, a satisfied groan erupting from his chest as he does. Deku is breathing heavily, but he’s conscious, which is more than they could say about last time. He leans back and tips his head back, closing his eyes and feeling sated for the first time in… however long it had been since he’d bit Deku the first time.
“Please eat,” Deku says, after both of them have calmed down and evened out their breathing a bit more. Deku is still on his lap. “In the future. And if you— if you need this, I really don’t mind. It’s okay.”
Now that his head is starting to clear up, he’s becoming more aware of just what exactly kind of fucked up situation he’s in. He yanks his legs apart so Deku tumbles off his lap and onto the ground.
“I’ll fucking eat,” he says, before Deku can protest being unceremoniously dumped on the ground. “Okay? I’ll be at my full strength so I can enjoy kicking your ass, shitty nerd. You don’t have to— we don’t have to talk about this.”
Deku looks— sad, almost, but Katsuki isn’t great at reading emotion, so he’s probably wrong. “Okay, Kacchan,” he says softly, standing up and making his way to the door, and he’s opened it and is about to leave when Katsuki groans and calls his name.
“Fucking— thank you, okay? Fuck.”
Deku smiles this time, so much nicer than the sadness he’d worn before. “You’re welcome, Kacchan,” he says sweetly, and when he’s gone Katsuki collapses on his bed and finally gets a good night’s sleep.
The third time he bites Deku isn’t until late in second year. They’re in Katsuki’s room because Deku fucking sucks at English, and because they’re like, friends now, maybe? Or something, at least. They’re something. Now that something a little bit dark shines behind Deku’s gaze, now that Katsuki’s learned how to communicate with something other than grunts and violence. He’s been trying to teach Deku grammar rules for hours, and he’s tired and hungry and he’s had to be stuck in his tiny room with Deku’s scent clouding his head the whole time, and eventually he snaps and slams shut the textbook and says, “Okay, you need to leave.”
“Wait, I think I almost got it! I’m sorry, please just put up with me for a few more minutes I swear—”
“That’s not— I mean, okay, you are really fucking annoying and I don’t know why you’re having so much trouble with these fucking tenses, but I’m hungry. Take a break, you can come back later if you’re that concerned about this test.”
“Oh, is that it?” Deku looks confused. “Eat, then, I don’t care.”
Why was he like this? “Just fuck off for twenty minutes, Deku, shit.”
Deku studies him closely. He does that sometimes, stares openly at Katsuki as if he’s trying to solve some kind of problem. It makes him feel incredibly torn open and seen, and he hates it, but he also really doesn’t hate it, and he hates that too.
“Are you ashamed to eat in front of me?”
“Are you really asking why I don’t want to suck down a bag of blood in front of you?”
“I’ve seen you suck down ramen, how is this different?”
Katsuki shakes his head in disbelief. “I really don’t understand what the fuck goes on in your brain.”
Deku closes his notebook and sits up on his knees, inching forward into Katsuki’s space. He leans away, but Deku follows. “If you don’t want to have a bag of blood, why don’t you bite me?”
Katsuki jerks away. “What the fuck, Deku?”
“I don’t understand why you won’t,” Deku says. “It’s clearly much better, and I’m giving you permission—”
“And you really think I’m gonna listen to you? Masochistic, self-sacrificial you?” Katsuki says, inching backwards to try and get away from Deku and that weird look in his eyes and his fucking smell, but his back hits his bed and he has nowhere else to go. Deku kneels in front of Katsuki’s crossed legs and leans in close, and Katsuki feels his fangs pop.
“I’m not offering to be sacrificial,” Deku says. “I’m offering because I want you to bite me.”
Katsuki’s eyes widen. “What the fuck,” he says again. It’s hard to speak around his fucking teeth. Deku’s eyes zero in on them when he speaks, and he lifts one of his hands, but then he stops.
“Can I touch, Kacchan?”
“What is wrong with you?” He mutters.
“That’s not an answer,” Deku says, patiently, normally, as if they weren’t talking about Katsuki’s fucking fangs and the fact that he needs to drink blood, and if Deku keeps telling him to bite him, eventually he’s gonna break and do as he fucking asks.
“Yes,” he growls out. Deku rewards him with a brilliant smile, and then he lifts his hand again, thick fingers probing gently at his fangs. Katsuki has the sudden thought that he wished Deku would shove those fingers in his mouth and down his throat.
Never mind Deku, what was wrong with him?
“Sharp,” Deku says under his breath, as if he hadn’t felt them in his fucking neck. “Do they only come out when you’re hungry?”
Katsuki swallows. He does not have the emotional intelligence to fully parse through everything he’s feeling right now.
He says, “Or when I’m around you.” He’s not sure why he says this, but he’s going to blame it on Deku’s scent so close, and the line of his neck as he leans over Katsuki.
“Why me?” Deku’s voice is quiet. His hand has fallen to Katsuki’s shoulder.
“You… smell good,” he admits. “And you—” Deku is so close. Katsuki leans forward and shoves his nose in his neck, inhaling deeply. He can’t hold himself back anymore. “You taste so good,” he says, and Deku grabs Katsuki’s legs and stretches them out in front of him so that he can straddle Katsuki’s lap, like they’d done the last time he’d bitten Deku. Katsuki grips his thighs, fingers digging into the hard muscle. “Better than anything.”
“Kacchan,” Deku says, right into his ear. “Bite me.”
He does. Sinks his fangs into Deku’s neck and feels that same addictive sense of relief as his blood washes over Katsuki’s tongue. Deku moans and writhes on Katsuki’s lap, arms locked tight around his neck as Katsuki drinks from him.
“Kacchan,” Deku says, but it doesn’t sound like a plea to stop— it sounds like he’s asking for more. Katsuki groans, one arm going around Deku’s waist to pull him closer, and as he does so Deku rolls his hips and Katsuki realizes that he’s hard.
He pulls away, lapping at the wound on Deku’s neck, and then he says, “Holy shit, Deku. You’re getting off on this.”
“Why do you think I kept asking,” he says furiously. Katsuki licks at the puncture marks on his neck.
“You fucking pervert, Deku,” he says, but he can’t hide the pleasure in his voice as Deku continues to grind against him. As if to prove his point, Deku drags Katsuki’s face up to press their mouths together, teeth and tongues clashing in a kiss that tastes like blood. When Deku pulls away for air his lip has been split open on Katsuki's fangs, and it's so hot, and Katsuki leans forward to lick the blood off of his lip.
“More,” Deku says into his mouth, and Katsuki moans and shoves Deku backwards off his lap, pushing him onto the ground and covering him with his body. He shoves his head to the other side to reveal the smooth, unblemished side of his neck. Deku hikes his legs around Katsuki’s waist, angling his head to give Katsuki better access to his neck. He rolls his hips down against Deku’s, and Deku rolls his up against Katsuki’s, and Katsuki leans down to sink his teeth into the unmarked side of Deku's neck. Deku lets out this stuttering little whine and he keens and jerks and then goes boneless beneath him, and Katsuki realizes that he’d fucking come. From being bitten.
“Holy shit, Deku,” he says, licking at the blood on his neck as he continues to grind down against him, and the wet stain he feels on the front of Deku’s pants pushes him over the edge. Deku whines at the overstimulation as Katsuki humps against him through his orgasm, and when he’s finished he rolls off of him onto the ground, chest heaving as he tries to catch his breath.
“What the fuck is wrong with you,” he asks again, weakly. Deku is also struggling to catch his breath.
“So much,” he says, and Katsuki throws his arm over his face and laughs only slightly hysterically.
“This is really fucked up,” Katsuki says.
“So are we,” Deku says which, point. They lay beside each other, trying to settle down, and Katsuki’s heart is finally starting to slow to a calmer pace when Deku says, “Do I really taste better than anything else?”
Katsuki flushes red in embarrassment. “Shut up,” he says, which is both not an answer and also an answer. Deku hums, but he doesn’t say anything, and he doesn’t mock Katsuki, and it lets him work up the confidence to ask, “What does it feel like?”
Deku thinks. “It— well, it hurts at first, when you break the skin, but after that it’s… it’s not bad. It doesn’t really hurt that much. It’s probably because of the coating on them.”
“The what?”
“There’s like, a coating on your fangs that acts as a kind of painkiller? Didn’t you know about it? Don’t you have Google alerts set up for the Vampire Villain?”
“Please tell me that’s not what they’re called.”
“It’s not the most original, but until they actually catch the person there’s not much to go on. Anyway, that’s one of the things they discovered after they started doing research on people who’ve been affected by the quirk. It numbs it, kind of, so after that initial burst of pain it actually kind of feels good.”
“Wait, you’re not telling me the bite makes you horny—”
“No!” Deku says. “No, no, it’s just a painkiller. The hornyness is just, um, me.”
“You’re so weird,” he says, but he rolls over onto his side and shoves his face back in Deku’s neck, licking at the wound again. Deku shivers and curls into him.
After a few really nice, wonderful minutes that he has to reluctantly call cuddling, Deku says, “Can I ask a bunch of really annoying questions about it now?”
Katsuki sighs. “You’re the worst.”
“Oh come on!” Deku whines. “I’ve been dying to ask for like, five years!”
Katsuki makes an annoyed sort of grumbling sound and then says, “Fine, but I’m not lying on the fucking floor the whole time.” He gets up and spreads out on his bed, and after a moment Deku clambors up beside him, slinging a leg over Katsuki’s and leaning up on his elbow to look down at him excitedly.
“Okay, so, when exactly did you get bit? I know you can still eat because I’ve seen you but does it do anything? Does it still taste good? And how long can you go without feeding? Does the blood taste like blood and you just like the taste now, or does it taste like something else? Can you control your fangs when they pop out? Have you ever had any other fresh blood? When you said I taste better what does that mean? Does it—”
Katsuki groans and drags Deku down to kiss him again. “I changed my mind. No questions.”
“Kacchan!”
Katsuki smirks at him. “How about this, if you answer the English questions right, I’ll answer one of yours.”
Deku whines. “That’s not fair, I hate English.”
“Take it or fucking leave it, nerd.”
Deku groans and sits up. “Okay, can we go over it one more time first?”
And just like that, they go back to studying. Katsuki feels sated and full and content, and he barely snaps at Deku for the rest of the night. “You’re way nicer like this,” Deku notes. “You can use me as a juicebox whenever you want if it makes you like this.”
“Stop trying to distract from how shitty you are at English.”
Deku pouts. It’s… cute. And annoying. “Okay, I’m ready. Ask me questions, but you have to answer mine after!”
“Get one right first,” Katsuki says. Deku smiles at him, wide and beautiful and still stained red with blood, and something very warm fills the spaces in Katsuki's chest.
"What does this… mean?" He asks before he can convince himself not to. Deku thinks about it.
"I can tell you what I… want it to mean?"
They're on Katsuki's bed still, sitting against the wall with their legs stretched out in front of them, thigh to thigh. Katsuki nods; Deku has always been braver than him.
"Okay, well…" Deku pauses, and then he swings around so he's in Katsuki's lap again. Katsuki isn't sure what it is with Deku and being in his fucking lap, but he sure as shit ain't complaining. Deku gets a feral sort of grin on his face, like he does when they're fighting. "I would like it to mean," Deku says, leaning in close so their lips are almost touching. "That you're my boyfriend now, and you can bite me whenever you want."
As Katsuki kisses him, he really can't decide which part of that he's more excited about.
The fourth, fifth, sixth, seventh time he bites Deku— well, eventually he just stops counting.