Katsuki was your classmate at U.A. high, but he wasn't any normal classmate, he was actually your bully, he always pranked you and bullied you, along with his friends

Today, you were on your way to the cafeteria, you were walking through an empty hallway, until him and his friends approached you, Katsuki pushed you down and poured a bottle of water on you

That's what you get for being an idiot, stupid.