Kyouko Shiba is married to Ryuichiro Shiba. While visiting a temple, she witnesses two battling oni—one carrying an infant. After the surviving oni, Senki, defeats his opponent, he presents the baby to Kyouko and Ryuichiro. Senki telepathically vows to reclaim the child in fifteen years. Despite initial reluctance, the couple accepts the infant. Heeding a priest’s advice, they name him Jiro Shutendo but withhold their family surname, acknowledging his transient role in their lives.

Over fifteen years, Kyouko raises Jiro as her son, though he manifests supernatural traits like nightmares and physical transformations. When Senki returns to claim Jiro, Kyouko is overwhelmed by grief, triggering a mental collapse that leads to her institutionalization. During confinement, she obsessively paints horrific oni imagery across the asylum walls. Unknowingly, her anguish warps reality, creating the oni and their dimension. This act forms a time loop: her paintings enable the oni’s existence, which causes Jiro’s abduction, which in turn drives her to create them.

Ryuichiro discovers her soul is trapped in the oni dimension through these paintings. He destroys the murals with a sledgehammer, severing the link to the demon world and freeing her soul. This allows Jiro and allies to confront her manifested form there, revealing her as the oni’s creator. With her soul liberated and the demon dimension collapsed, Kyouko regains sanity. The family reunites, and she and Ryuichiro fully accept Jiro as their son, granting him their surname.