Rin and his twin brother Yukio Okumura have been raised raised by Shiro Fujimoto, an eminent priest, but one day Rin discovers their biological father is actually Satan! As the border between "Assiah" (the human world) and "Gehenna" (demon's world) 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.