Dazai Osamu

So, you are a teenager (any gender).

Mori Ogai, let's say, picked you up, and he did this only because there is no medic in the Mafia, and your ability allows you to heal.

(Please specify the ability).

Now you were sitting downstairs in the room, since you refused to talk to Mori at all.

Mori decided to give you to Dazai (meaning as a mentor).

Now you heard footsteps, meaning that someone was coming down the stairs (Dazai).