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The last thing Katsuki sees before the smoke hits him is Izuku's worried face. Then he inhales the villain's fucking quirk and starts to cough, and when he opens his eyes he sees...
Izuku's face. Something almost poetic about that, huh? The first and last thing he sees.
Katsuki doesn't have time to think about this, because as soon as he absorbs the scene in front of him (Izuku cowering against the wall; his own younger self looming over him with a palm raised), Katsuki is moving. He doesn't stop to think about the potential consequences, but then again he rarely does. All he sees is Izuku in trouble, and his body—
Heh. His body just moved on its own.
He grabs his younger self by the scruff of the neck and hauls him away from Izuku, slamming him up against the wall. His younger self struggles, at least until he opens his eyes and sees who his attacker is. Izuku reacts in much the same way; ever the hero, he grabs Katsuki's arm as he tries in vain to haul him away from his younger self.
"Leave him alone!" He shouts, until he catches sight of who the attacker actually is. "K-K-acchan?"
Katsuki does his best to ignore the way this entire situation would be a therapist's wet dream if they could see it. He slams his younger self against the wall again, and he feels a phantom pain in his skull, like an old wound flaring up.
"Fuck off!" His younger self shouts. "If you're me why are you fuckin' attacking me?"
"'Cause I'm a hero," Katsuki snarls. "And that's what heroes do when they see villains attacking quirkless little crybabies." Oops—habit. It wasn't not true, though.
"You're a hero," his younger self says in awe. Katsuki's lip curls.
"No thanks to you," he says. He raises his palm and is just about to give himself a taste of his own medicine when—
"W-wait!” Izuku grabs his arm again, tries to pull it back. "Kacchan? S-sir, please, don't hurt him."
It takes Katsuki a moment to realize he's ‘sir’. Fuck. He feels like his father.
He gives Izuku a look. "After everything he's done, you don't want me to hurt him?"
Izuku shakes his head. Katsuki sighs and lets his younger self drop to the ground. Leave it to lzuku to always be the best.
His younger self looks like he's about to start a fight that he will definitely lose, but then he seems to fully register what he's seeing, and a look of amazement plasters itself to his face. "That's my design," he says, looking at Katsuki's outfit. "Those—those are my gauntlets." He looks up in excitement. "What's your hero name?"
"None of your damn business!" Katsuki yells, which is perhaps not strictly true. He'll blame it on not wanting to give away secrets to the future, instead of admitting that he's being petty.
His younger self glares. "How do I know you're really me? You don't seem like me. Get away from him, Deku."
This last part, the misplaced protection, serves to anger Katsuki more. He upturns his palms and lets off his quirk.
"Don't test me, kid," he says. “I'm you. Got hit by some quirk and got sent back here. Now get the fuck out of here."
His younger self's eyes narrow, and his eyes flick to Izuku.
"It's okay," Izuku says. "It’s just Kacchan, right? You don't have to be worried, Kacchan."
It's the wrong thing to say. His eyes narrow, and he looks on the verge of physically stomping his foot. "I'm not worried!" He shouts. "Like I'd ever be worried about you, stupid Deku!" Then with one last incensed look at the two of them, he turns and stomps off.
Katsuki watches him go with something tight in his chest. He wants to follow, wants to tell him all the mistakes he’s going to make, wants to put him on the proper path early—but he knows that he can’t. Whether this is some kind of time travel quirk or a parallel universe or something, he can’t interfere much with the past. Which means he definitely shouldn’t do what he’s about to do.
He kneels down so he’s more on Izuku’s level and he says, “Hey. Wanna grab something to eat?”
He takes Izuku to a ramen shop near Aldera and tells him to order what he wants. Izuku watches him with wide eyes the whole time, and even when his food arrives, he continues to stare at Katsuki with the same wide eyed expression. Katsuki eats a mouthful of his own noodles and then says, “Auntie never tell you it’s rude to stare?”
Izuku turns red and looks down at his food, hands in his lap. “S-sorry,” he says. “It’s just, really surprising to see you like this. H-how old are you? I m-mean, when are you from?”
“I’m twenty-six,” he says. Izuku’s mouth forms an ‘O’.
“And Kacchan’s a… a hero?”
Katsuki grins at him. “You’re damn right I am.”
Izuku grins back. “Kacchan’s amazing! I always knew you’d reach your dream, Kacchan! I bet you’re the best hero!”
“Wanna know something even cooler?” Katsuki asks, and Izuku nods in excitement. Katsuki leans forward and says, “All Might was my teacher.”
Izuku rears back and stares at Katsuki in open wonder. “No way!” He says, eyes bright. “You know All Might, Kacchan? He was your teacher?” Like a broken record.
Katsuki nods. “You gotta promise not to tell anybody anything, okay? I shouldn’t be telling you shit. But—” Katsuki owes this kid so much. He can’t just not do anything—he has to seize the opportunity in front of him. “I met All Might. And you wanna know something? You do, too.”
Izuku’s eyes fill with tears. “I-I do?”
Katsuki nods. He has to tread carefully here, can’t give away too much, but surely a little bit won’t hurt. Just enough to get Izuku through the next few years, a promise that something more is coming.
Izuku looks down at his lap again; he takes a mouthful of his food and chews slowly, and when he’s done he says, “Can I ask Kacchan a question?”
Katsuki nods. “Can’t promise I’ll answer it though.”
“Are—in the future, do we… do I…” He takes a deep breath and then blurts out, “Are Kacchan and I ever friends again?”
Katsuki’s heart breaks in his chest. He wants to stomp home and beat the shit out of the idiot Katsuki that’s there right now, who doesn’t understand that he’s so goddamn lucky to have Izuku in his life, who’s going to spend the next years being put in his place over and over and over. On the other side of it, Katsuki doesn’t envy him the journey he’s going to have to go on.
And Izuku, too. Looking at him, Katsuki is blown away at how young and innocent he is. No scars on his body, no haunted look in his eyes. Despite everything he’s been through, all the cruelty he’s been on the receiving end of, there’s still such joy in his face.
Katsuki wants to tell him the truth, that friends is nowhere close to describing what he and Izuku are; that the bond between them has been forged in blood and war and fire, that it’s unbreakable. But he knows he can’t, both because he can’t tell Izuku too much about the future but also because he can’t explain in words what Izuku means to him. The closest thing he could possibly do is put the kid's hand to his chest, so he could feel the beating of Katsuki’s reconstructed heart, and he could say, this is what we are.
But he can’t; he doesn’t. Instead he just nods and says, solemnly, “Yeah, kid. We’re friends again.”
A wide, watery smile breaks out across Izuku's face, like being friends with Katsuki is his life's dream come true. He really doesn't know what he ever did to deserve Izuku in his life.
He starts to feel strange, suddenly, a tingling in his fingers and toes, and he thinks this is probably it for his jaunt to the past. He fishes out a handful of cash which he lays on the table so he doesn’t disappear and leave Izuku with a bill that he definitely couldn’t afford. Then he grabs Izuku’s hands, fucking tiny in his own, and he says, “It won’t always be like this, Izuku.” At the sound of his given name Izuku’s eyes widen again. Katsuki’s surprised they haven’t gotten stuck that way.
“Kacchan, wait!” He cries, as if Katsuki has any say in the matter. “What’s your hero name?”
Katsuki grins—he’s definitely not ruining that surprise. “You’ll have to wait to find out,” he teases, and Izuku’s wide smile is the last thing he sees before he fades away.
The first thing he sees is Izuku’s worried face. The exact same worried face he’d been wearing when Katsuki left. Katsuki wouldn’t be surprised if it stayed in that position the entire time Katsuki was gone.
He’s where he was when he got hit by the quirk; he’d been gone about two hours, all in all. Izuku rushes at him as soon as he sees him back, and despite the amount of people there—including, no doubt, the press—he throws his arms around Katsuki’s neck and hugs him.
“I remember,” he says into Katsuki’s ear. “I remember that day. I remember what you said.”
Katsuki hates time travel quirks. They’re just confusing. But he hugs Izuku back, ignores the people around them and wraps his arms snugly around Izuku’s waist.
“Thanks for sticking with me even when I was a shithead,” he says. Izuku laughs into his skin.
“Always, Kacchan. I’ll stick by you always.”