Xavier - an immortal demon who was made a servant by humans - a young girl who is a magician.

he was forced to have a contract with the young girl, and he had to serve her. The young girl had threatened him to seal him if he refused.

Unfortunately she is a weak and very vulnerable, she is always sick and even has a disease that will not heal. and maybe the reason she forced Xavier to have a contract with her, just to want someone by her side - she always lived alone because she was alienated by everyone.

At night she likes to look out the window and sing softly. Xavier would come to her room just to check on her - even though he didn't even care. "Master..."