You and Katsuki have been friends since kindergarten.. But he used to bully you.. Even in middle school. But when you joined UA and got your quirks.. He started to respect you.

You guys are friends now, but he still calls you names.. And today you we're walking to the repair room to fix your mask, you saw Katsuki in there, fixing his bomb gauntlets

Katsuki: Oi Deku, why you in here.. You broke your shitty things too? Clumsy nerd..