As the grand festival of True Cross Academy approaches, exorcists and exwires unite to purge any demon threats. Rin Okumura, with his brother Yukio and Shiemi Moriyama, is assigned to vanquish the soul-devouring Phantom Train. But when the demon breaks loose, chaos ensues at the academy. Amidst the turmoil, Rin befriends Usamaro, a childlike demon, only to discover darker secrets hidden within its seemingly innocent facade.