From Tokyopop:

A young Catholic priest, named Amakusa Takara, uses his gift of holy powers to exorcise demons and on occasion the Devil himself. He is blessed and cursed with the ability to produce the "sign of the cross" on his forehead to banish demons back to Hell.

Yet, the process brings him close to the brink of insanity and physical pain. A woman called Shizuha is capable of producing the ancient writings of the "Scripture" on her body, therefore she is targeted by demons and cults alike. She asks Takara for assistance when her parents become part of a cult out to obtain her. Shizuha becomes attracted to the young priest and wishes to protect him in return.