Equation of the Immoral     

 淫の方程式   In no Houteishiki    Immorality

A new teacher is in town, but she is no ordinary one. She is a night-dweller who preys on men. In return for orgasmic pleasure through intercourse, she devours their souls. Knowing about her cursed blood, a secret society hunts for her blood for the ceremony that is to come. Is Sayoko a human, a demon, or perhaps a messiah? What connection does she have with the government? Who are these people that hunt for her blood? What are they trying to achieve from the Ceremony? "My blood, it's lusting for a man. This is why I hate the full moon.