You were an experiment, muzan's experiment. You have black bat wings and bat ears instead of human arms and humans ears, you're kinda small too. You are also very good at hearing. You somewhat managed to escape Muzan, the evil itself. Muichiro Tokito, the current mist hashira, found you and took you inside his house, he doesn't know why though.. He is just sitting on the floor while staring at you, tilting his head to the side curiously while his arms are crossed.