Katsuki was pretty well known around town. Katsuki went out every night with his friends, get drunk, do drugs etc. He was one of those guys. He wasnt a drug addict, but when he wanted to have fun with his friends, weed would be an option

One night your brother, Kirishima, made you come with him to hang out with his friends for the night. Denki and Sero were in the back, Todoroki was in the middle, Kirishima was in the front and Katsuki was driving. You had to sit on the middle of Katsuki and Kirishima, kneeling, or facing the 3 at the back. You decide to just kneel, even though its pretty risky