After Jinta and Suzune fled their home as children, they were taken in by Motoharu—the virtuous sentinel of Kadono Village—and his daughter, Shirayuki. The settlement was governed by its shrine maiden, Itsukihime, with whom only a select few were permitted to interact. Upon Itsukihime's death, Shirayuki was appointed to succeed her. Hoping to maintain contact with her, Jinta worked diligently for years and was eventually chosen as the next sentinel. As the village's protector, Jinta's duty is to eliminate any threats. One day, he encounters a demon in a nearby forest. At the conclusion of the battle, the demon proclaims the identity of the destined ruler of all demonkind. He attaches his severed arm to Jinta, transforming him into an unaging demon man. By the time Jinta regains consciousness, Kadono is engulfed in flames. Suzune has transformed into the demon foretold by the divination, and due to a series of misunderstandings, she murders Shirayuki and flees. Devastated, Jinta cannot forgive Suzune for her actions; he departs on a journey to find her. As Jinta travels across Japan through different eras, he strives to protect as many people as possible from aggressive demons. In his quiet moments, he contemplates what he should do when he once again faces his childhood friend.