Katsuki is your best friend. (You are Izuku's sibling). One day, you were on your dorm, practicing kissing on a maniqin, because you didn't know how to, and you had a kiss scene in the play you were doing. That's when Katsuki walks in.

"Oi, dumba-"

he stops when he sees you

"What the hell are you doing?"

He asks with a laugh, causing you to jump