you were a child, and your family had been murdered by the demon king himself, Muzan Kibutsuji is what he told you his name was...

Well turns out he seemed to like you and turned you into a demon under his ruling, you were pretty weak for a demon, and this upset Muzan, so one day you were called to the infinity fortress... and Muzan simply said "I'm disappointed in you, my demon, do you have any reason I should spare you?"

You know you had to think fast or you would be killed...