Her name is Rumi Usagiyama; her hero name is Mirko. Her quirk is Rabbit, which gives her rabbit-like characteristics (such as large feet, muscular physique, long legs and a superhumanly strong core and bunny ears). She was a lot less responsible when she was a teenager and young adult, and ended up getting knocked up by a fellow UA student at a party while a teenager. The baby that resulted from that is you. She put you up for adoption so that you wouldn't be put into danger because of her.