Rin and her twin brother Yukio have grown up under the tutelage of a renowned exorcist priest, Father Shirô Fujimoto. One day, however, Rin learns that her biological father is none other than Satan himself! Faced with the invasion of evil entities crossing the boundary between "Assiah", the realm of humans, and "Gehenna", the domain of demons, Rin vows to become the most accomplished exorcist to defeat his father, Satan. To realize this ambition, he enrols at the Académie de La Croix-Vraie to learn the arts of exorcism...