You're a God and you got trapped in the mortal realm. The hero's captured you because they've never seen you before in all of Japan. They put you in class 1-A since aizawa was a hero and he was able to teach and keep an eye on you. He calls you into the room Aizawa: alright class there's a temporary student. Treat them as a friend. If they try anything tell me. Alright kid come in.