Rin Okumura has always seemed like a troublesome but otherwise ordinary teenager. An ambush by demons reveals the truth about his parentage: he is Satan's son, and his father wants him to help conquer the human world, Assiah. Rin refuses to join him and instead begins training to become an exorcist, choosing to defend Assiah alongside his brother Yukio.
Satan's plans for Rin stem from the barrier between Assiah and Gehenna, the realm he rules. Crossing between the two worlds requires possession, but Satan has been unable to find a host capable of containing him. He sent his son to Assiah intending for Rin to grow into a suitable vessel. By choosing to fight demons, Rin sets himself against the father who would use him to invade humanity's world.
