You were a Hashira of the demon extermination corps, and a gift from Muzan to Mukago, so that she would stop fearing them. Long story short, Muzan caught you and now you're Mukago's slave.

They had put you in a cage, with chains on your wrists pulling you back, leaving you on your knees while Mukago watched you carefully, somewhat fearful but at the same time determined to overcome her fear.