Chapter Text
There’s been a lot of people that have called Izuku crazy. Bakugou– obviously–, other classmates, bitchy teenagers, annoyed adults. And sure, maybe Izuku’s a little strange. But mostly he’s just quiet, merely someone who lets his thoughts run for maybe longer than necessary and the thoughts sometimes become words. Izuku doesn’t see that as crazy. If anything, Bakugou’s constant yelling could be seen as crazy. He does mumble a lot, he supposes, and talks to himself sometimes and he gets lost in his head– but he doesn’t see that as too weird, even if it is a little annoying.
That is, until his head starts talking back.
The first time it happens is when he’s on his way back to the dorms, mourning his almost-normal snack run. He’d actually managed to leave the store with his snack, relatively unharmed (except for his dignity- an old lady had grabbed his chips off a high shelf for him. god, why is he so short), but then a man with salt-and-pepper hair and ram’s horns had smacked directly into him.
“Oh, if it isn’t a baby hero from UA!” the man had cooed, his voice deceptively high-pitched. He tossed his head in a very ram-like motion. “Midoriya Izuku, mhm, that’s right!”
The man’s hand had snapped out, faster than Izuku anticipated, and latched tightly around his wrist. Izuku jerked a bit in surprise, but kept himself from lashing out. It wasn’t the first time he’d been recognised, of course, but the wrist-grabbing was new. “Uh, sir,” he said, making sure his tone was polite, if cautious. “Would you let go of me, please?”
The man acted like he hadn’t heard Izuku. “Baby hero, who thinks he’s ready for the world…but does he know of the real world? Of the ugly, ugly reality of consequences, of cause and effect and what must be done to ensure safety? Hmm…”
Alarm bells sounded in Izuku’s head, nerves reverberating along his body. Stay calm, he told himself. He might not be a threat. He tries to pull away as gently as possible. “Excuse me, sir, but I, uh, have somewhere to be,”
The man’s grip only tightened. Now Izuku is truly wary, adrenaline pumping along with his heart. He lurches backward, ripping his arm out of the man’s grasp. The man doesn’t move, but clicks his tongue in annoyance. “Now, now,” the man chides. “No fighting here, we promise. Just a lesson. Which one…? Ah, yes.” Both of the man’s hands shoot out this time, grabbing onto Izuku’s shoulders, fingernails digging into the fabric of his shirt. Izuku cries out, trying to twist away.
“Don’t worry,” the man tells him serenely. “You will understand soon.”
A jolt zapped through the man’s fingers, dancing along Izuku’s nervous system and rattling him to the bone. The world swayed, shifted, turned upside-down around him and god, he couldn't breathe, what did he do?– and the next thing he knew was concrete biting into his knees and nausea roiling in his stomach. The man was gone. His grocery bag had been moved to right in front of him, the cheery yellow smiley face peering into his soul.
I’m never going to be able to live this down if the class finds out, Izuku thinks miserably. He peeled himself off of the sidewalk and hoped he could get back before Aizawa-sensei formed a search party.
He’s a few feet away from UA’s gates when he proceeds to trip over his somehow magically untied shoelace and stub his toe roughly on a rock. He thinks, Fuck my life, as he hops around in a miserable, one-footed circle of pain.
He proceeds to almost fall over as a voice that is definitely not his echoes in his mind. What?
What? Izuku thinks back automatically, just as baffled as the voice.
Who...? the voice stammers. It’s masculine but young, maybe somewhere around Izuku’s age. Izuku and the voice appear to have the same realisation at the same time.
There’s someone in my head! -dammit what was that demon’s Art?- oh my god how the hell- wouldn’t it be cancelled when I killed him? Is this a curse?- stupid snack runs, I’m never leaving my room again. What quirk would even- what is going on?
A sudden, piercing headache roars between Izuku’s ears, and his hands fly to his head. He takes a few deep breaths, waiting for the pain to abate. He shakes his head, hard (as if that will do anything) and tries to sort out what was his thoughts and what was the voice’s. The headache is lessening to a dull throb when the voice demands again, What is going on?
Izuku jumps, head twisting as if he can find the person the voice is attached to. I don’t know! He only-slightly-shrieks. You killed someone?!
No- I- yes, but it was a demon! The voice only-slightly-shrieks back. It was going to eat me!
Why the hell would a demon eat you, they don’t even exist!
I know a lot of people don’t think they exist, but I promise they do and it’s my job to kill them so they don’t kill anyone else!
What, Izuku thinks intelligently. Okay, what the fuck. What the fuck is happening. Was it that man’s quirk? Was his ‘lesson’ sticking some insane murderer spouting about demons into Izuku’s head so he could learn ‘the reality of consequences’? Consequences for what? For bumping into him on the sidewalk? That was so the man’s fault, though, he’d run directly into Izuku! He just wanted some goddamn snacks, why is it always him?
He glares into the security camera on the gates, sure that Nedzu is in his office laughing at him right now. Izuku buries his face into his hands, groaning. “Oh my god. Aizawa-sensei is going to kill me. I’m dead. I’m in the grave, six feet under because someone stuck a person in my fucking head,”
…it wasn’t your fault? The voice tries. I mean, from my perspective you were the one thrown into my head. Then, after a few seconds, a twin horror to Izuku’s seems to dawn on the voice. Oh, no. Giyuu-san is going to be so angry. Damn, what have I gotten myself into?
“You and me both,” Izuku mutters, finally flashing his student ID up to the sensor and dragging himself onto campus.
Kaminari skids into the entryway when Izuku shuts the door behind him. “Bro!” the blond says jovially. “The sustenance has arrived!”
Izuku dislikes how that sentence makes him seem like the sustenance, but whatever. He deposits the bag of snacks with Kirishima (after snagging his own, of course) and quickly retreats to his room before anyone can tease him about having successfully returned to UA in one piece.
Technically true, the voice muses. Just…with a plus one.
Oh, shut up, Izuku thinks, though not unkindly. He allows himself to flop dramatically on his bed, limbs starfishing over his comforter. He shoves his face into his comforter, trying not to think about how there’s another person in his head, listening to his thoughts and oh god they’re going to know so many embarrassing things, damn- but at least it’s a stranger and not, like, Uraraka or something. That’s a plus, he supposes (if there’s any pluses to be found in this situation).
This is…so weird, The voice mumbles. He sounds almost as distraught as Izuku. The voice’s thoughts speed up, going over theories about a demon’s…art? and going over spells he’s heard of or experienced and it's easy to say that Izuku is thoroughly confused.
So you're serious about the whole demon thing? Izuku asks, trying very hard not to look at the assignments waiting for him on his desk. And…spells? Like magic?
Magic? the voice repeats musingly. No- well, maybe? Some demons grow so powerful that they can cultivate their own Demon Art, which is like a special ability that they use to kill more humans and slayers.
Wait, ‘special ability’? You mean quirk, right?
Quirk? the voice says the word hesitantly, like they’ve never heard of it before. It’s then that Izuku realises what’s been nagging him about the voice; he has a soft accent, something similar to Japanese, but not quite. A different dialect, maybe? I don’t think I know what that means. As far as I know, demons don’t have, ah, quirks.
Izuku sits up, all potential thoughts of homework forgotten. You don’t know what a quirk is?
…no? Should I? A fast thought flies through the voice’s head, but Izuku can’t quite catch it. Something about a dense pig? Hold on, I have to-
The thoughts following consist mostly of swearing, starting out mild and crescendoing into some truly impressive specimens. Izuku rates it as an 8.6 on the Kacchan scale. It’s not entirely clear what he’s cursing about- he’s shouting at a Zenitsu and a boar? A boy? A boar-boy?- but something is clearly going down on the voice’s end. Izuku pities the poor bastard who’s invoked the voice’s wrath.
Meanwhile, he sorts through his assignments, putting them into two piles: ‘half-ass at the last minute and still get at least 87%’, and ‘should actually put effort into’. Sadly, the latter far outweighs the former. That’s UA for you, he supposes. He’s personally doubtful of his classmates’ claims that he’s a genius (he likes analysis, not fucking quirk history), but academics have never really been a challenge for him. Izuku can count on one- no, wait, zero hands- people who’ve appreciated that about him enough not to punch him.
Sounds fun, the voice grumbles, sounding distinctly harried. He sighs, which is weird to hear from inside someone’s head. Sorry. A couple of injured idiots tried to fight each other over fish. What were we talking about?
Um, quirks. Izuku abandons his homework. But actually, I should probably ask what your name is. Can’t keep referring to you as ‘the voice’.
Oh! Sure!, the voice agrees surprisingly quickly for a potential deranged murderer. His voice does sound nice, though. I’m Kamado Tanjirou!
Cool. Nice to meet you, Kamado-san. I’m Midoriya Izuku. Izuku really hopes giving out his identity isn't going to come back to bite him in the ass. This could be an elaborate villain scheme, but Kamado-san seems honestly too sincere and not villainous. Also, it would be a really weird way to try to, like, kidnap Izuku or something. Again, hopefully.
Kamado-san politely ignores Izuku’s train of thought. Oh, you can just call me Tanjirou!
Uh, okay. Just call me Izuku, then. Izuku rolls his eyes, then wonders if Tanjiro could tell that he did that. Probably good to get that out of the way now, right? God knows that’ll probably be the least of the personal information that’ll be up front and personal.
Tanjirou laughs softly (don’t ask how Izuku knows that. He just does). Yeah, you’re probably right. Any idea how long this will last?
Not a clue.
Wonderful.
~ - Omake - ~
Tanjirou takes a deep breath as he cleans his blade, letting the swell of oxygen slow his heart and relax his muscles. The demon hadn’t been particularly difficult, but it had a strange splitting ability, almost like the first demon he had fought. Thankfully, it only split into two, even if one of its forms was child-sized.
Inosuke cackles triumphantly from beside him, swinging his blades in a way that might have taken off Zenitsu’s hand if the blond hadn’t scooted away. “Take that, shitty demon! No one will weep over your smouldering pyre, and only the laughs of the victorious shall follow you to the afterlife!”
Tanjirou feels his lips twitch, though whether it’s to smile or to frown, he isn’t sure. “That’s..nice, Inosuke,” he mutters as he bows to the fragmenting shards of the demon, sending a mental prayer towards their departing soul. He turns back to his companions, wincing at the sight of Inosuke’s shoulder wound.
“Stop looking at me like that, stupid freak!” Inosuke snarls.
“I think I have some bandages, just hold on a sec,” Tanjirou tells him pleasantly. He’s had far too much Inosuke exposure to be fazed by the boy’s words. He’s rooting through his pack when a strange…buzzing sensation crawls across his skin. He almost drops the bandages as the feeling intensifies, shrieking as it spirals through his blood. The ground rocks, suddenly unstable beneath his feet and he stumbles. His ears ring, ring, ring-
Fuck my life.
Tanjirou blinks. Brings a hand to his head, checks for blood. No pain greets him, however, meaning that a head wound is not the reason for the words echoing in his skull. He thinks a startled, What?
What? The voice repeats. Tanjirou whirls around, sword leaping to his hand, but there’s only forest surrounding him.
He forces his breathing to smooth out. “Who…” he starts, and it’s the sound of his voice, strangely loud and real, that sends the realisation hurtling at him: there’s someone in my head.
A roaring jumble of combined thoughts is cut short by pain stabbing into Tanjirou’s head. He grunts and staggers at the onslaught, trees blurring into mottled greens around him. Zenitsu lets out a cry and races forward to steady him, amber eyes already welling.
As Tanjirou comes to terms with the impossible reality of what’s happening, he wholeheartedly agrees with the voice’s first statement: Fuck my life.