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Izuku has a secret. One he hides so carefully, he won’t even allow himself to think about it. It’s not like he’s running away from it. He just doesn’t know why he did it.
When it happened, it just happened. There was absolutely nothing wrong with it for him, when he did it. But in hindsight, it shouldn’t have happened. See, you don’t just kiss your sleeping childhood friend. Even if Izuku was only five back then, he knew you only kissed people you loved.
So why did he kiss Katsuki? Izuku loved Katsuki obviously, but that was more love out of admiration and innocence than romantic love.
Now after seeing Katsuki so vulnerable for the very first time, Izuku can’t stop thinking about all their past interactions and exactly how wrong he had perceived Katsuki’s behaviour and how that lead to the loop of misunderstandings they ran around in.
Inevitably his mind goes back to when he kissed Katsuki as children. For God’s sake, it was an innocent act and he shouldn’t tarnish it with bad thoughts, but he just can’t help feeling embarrassed over it. Embarrassed and stupid, because why did he do that?
Izuku risks a glance at Katsuki, hoping he hasn’t picked up on Izuku’s weird gesturing with his hands. Izuku is an open book and the last thing he needs after such an eventful night is a conversation about kisses.
He feels immensely relieved to find Katsuki sleeping on the couch. After the fight and the following scolding from Aizawa, they both wanted to catch their breaths in the common area, before attempting the stairs. The wounds really hurt, especially the side Katsuki punched him in.
Izuku collapses down onto the couch and massages his side. He’s going to have a very uncomfortable night. He stretches his whole body out and then lays back, staring at the ceiling. His gaze drifts to Katsuki, who is sitting, head barely supported by his shoulder as he sleeps. And now that he already recalled the memory, he inevitably thinks about it again.
Izuku rubs his face with both his hands and determinedly stares at the ceiling. He tugs at his hair and tells himself to just stop thinking and sleep as well. Only, his mind is working against him, so he inevitably glances over again. Which is horrible because that leads to him carefully sitting up and then standing, to loom over Katsuki’s sleeping figure.
Since he did it once, a second time wouldn’t hurt anyone right? And it’s not like he has ulterior motives, he’s just overwhelmed from the revelations and he can’t possibly be thinking straight. No, he really isn’t.
So Izuku braces himself with his hands on either side of Katsuki’s sleeping figure and leans in. He makes it very quick, just a little peck, really. Nothing to write home about but enough to make him stop staring and thinking about it.
Then he draws back and sits on his own couch again, back to staring at the ceiling. Suddenly he’s feeling twice as stupid as before. Why would he do that again, after agonising so much for doing it as a child? The desire is completely irrational.
Is it the lingering adrenaline? It must be because he kept thinking of the past and then had an opportunity like this and just… tried to relive it? Which doesn’t make sense, even to him.
Izuku sighs and glances at Katsuki, only to find Katsuki’s eyes steadily on him. Izuku goes cold all over. Was he awake the whole time? “K-Kacchan?”
Katsuki stares at him for a while longer before he talks. “We talked way too much today. I’m past my threshold, Deku. I’m going to bed.” He stands up and starts towards the stairs.
Only, Izuku is suddenly on his feet and has a hand on Katsuki’s arm. He’s not sure what he wants to say before he opens his mouth. “You were sleeping,” he says. He sounds desperate to his own ears, but he just has to make sure.
Katsuki glances at the hand on his arm before meeting Izuku’s eyes. “Which instance are you talking about?”
Izuku takes a step back because no. Katsuki was definitely asleep. He was, Izuku is sure of it. Yet, Katsuki keeps his eyes steadily on Izuku. He wants to sink down into a hole and never face Katsuki again. “Oh god.”
Katsuki sighs and turns around. “Back then and just now, both times you looked perplexed after you did it. You stupid ass don’t even know why you do the shit you do.”
Izuku can’t even deny that. He only has excuses for his behaviour and while they may work for his actions as a child, they don’t work for his actions now. So, he closes his eyes and admits, “I don’t. But I’m going to figure it out!”
“I don’t care.”
“But I do. And once I figure it out, you will have to tell my why you kept knowing it a secret back then, and why you did not react to me kissing you just now.”
“I’m tired.”
“Has never stopped you before.”
Katsuki doesn’t reply while Izuku watches him walk up the stairs, disappearing from view. Suddenly all his energy is gone, and he finds himself crouched down, hugging his knees to his chest. Izuku doesn’t understand himself anymore. Just where did all he say come from?
That doesn’t matter now. He just has to sort out his thoughts and then he will make good on his words. He’s not sure what will happen next.
All he knows is that Kacchan knows all his secrets.