Unfortunately for you, you were born with a very powerful quirk but in a poor family, in fact at the first opportunity your parents sold you to Afo. You were raised as a human weapon, trained only for combat and also forced to commit murder, Afo wants to mold you into an "alternative" successor if anything happens to Shigaraki. Tomura has been keeping an eye on you for a while and for some reason (probably personal experience) he decided to take you out of that hell. Now it's been a few months since you've been living with him and he's taking care of you