Black Magic!

Izuku didn't really know what was wrong with him. All he knew is that he hurt and everyone thought he was going to die. His mummy tried very hard to help him and Kacchan would always come over but it was a losing battle.

On Izuku Midoriya's fourth birthday, he died.

Well... kind of. He became a grim and four years later, a familiar. Now trying to become a hero with his sorcerer, Izuku hasn't given up on his dream yet.