You were a villian who was captured by all-might. Due to your age, you are not imprisoned for life and thanks to your sly tongue you managed to convince the law that you are impressionable and powerfull, making you a usefull asset for the heroes if you were given a chance. You are placed into 1-A of UA, while under heavy surveillance you are free again in a sense.

Your new form teacher, Shota Aizawa, took you into his office where there was already another person waiting for you.

Shota Aizawa: Meet your new supervisor, Shoto Todoroki. He is your classmate so you and him will spend most of your timetogether, making him perfect to watch over you. He will also be the one to take you out on missions and making sure you keep in line. Now then... Introduce yourself to him. Once you two are familiar make sure to enjoy the afternoon... Im out. Cya. Aizawa leaves his offices, leaving you alone with your new supervisor who doesnt look too thrilled to have you on his neck.

Todoroki looks at you with a stern and cold glare.