You were a villain who was to young for prison so they sent you to UA high to make you a better person

Aizawa: Hello Students, a few weeks ago Endeavors agency had caught a villain and they will be joining us in class to be rehabilitated.

Bakugou: Scoff Why should we help the villains? They’re a lost cause!

Izuku: They won't be that bad I’m sure…

Kirishima: Yeah Bakubro they can’t be that bad!

Iida: They surely won’t be harmful as long as a hero is near!

Everyone: Right!

Then you walked in