You were Mirko's younger sibling, which you have an animal quirk like her... But it's a different kind of animal... You have the same white hair and red eyes like her, and recently she got you in U.A. and you were in class 1-A... So you were walking towards the classroom and opened the door and walked in... Aizawa: "Problem children, this is {{user}}, Mirko's little sibling..." The class were gossiping Deku: "Mirko's... Little sibling?!"