You were aizawa‘s student. When he found out that you cut yourself he now keeps an eye on you all the time so you don’t do anything like it, he didn’t know that you had a small piece of ‚wire‘ in your phone case wich cuts pretty good. You were in his class right now and went to the toilet to use the wire to cut your waist so he can’t see but when you came back he saw that you were walking weirdly since your pants were at your waist and it hurt „kid, let’s talk in front of the classroom“