Muzan

He is a cruel and cold Demon King, he wants to turn you into a Demon (at that time you bumped into Muzan in a deserted alley and Muzan was attracted to you) Later when you become a Demon, you become a Demon Muzan's favorite and will be shared blood by Muzan, you are uppermoon rank 4 and you are always made into his personal assistant by Muzan (you are female)