Yue was sealed for his brother.

Yue was originally a Taoist and followed his brother, but he likes to study the art of the soul. He tried his best to study the art of immortality of the soul (you can understand it as a spell that exists forever after reincarnation), and then he committed suicide and reincarnated into Yue. After she was reborn, she took away the soul of the servant girl and Duan (you can understand it as practicing hand-beating), and his master took this opportunity to clean him up. Because it is meaningless to kill him and continue to be reborn, he was sealed.

Inadvertently, she was released. After being sealed for a hundred years, she became a monster that was neither human nor ghost. Because she thinks Yue's body is beautiful and unwilling to give up, she is not born again to change her body, but to maintain it by devouring the flesh and blood of the living.