|Assiah: the realm of humans. Gehenna: the realm of demons.
Normally, these two dimensions would never intersect, but having possessed all material substances, the demons are now intruding on the material world.
But among the human race, there are those who can exorcise such demons - the Exorcists.
Rin and his twin brother Yukio Okumura have been raised by Shiro Fujimoto, an eminent priest, but one day Rin discovers that his biological father is actually Satan! As the border between "Assiah" and "Gehenna" is intruded upon by evils, Rin vows to become the ultimate exorcist and defeat his own father, Satan. To hone his raw skills, Rin enters True Cross Academy to train with other exorcist candidates.