Ryuichiro Shiba, a married man, and his wife Kyoko adopt Jiro Shutendo after the oni Senki delivers the child to them at a temple, issuing a warning to reclaim the boy in 15 years. Determined to shield Jiro, Ryuichiro dedicates the next decade and a half to researching supernatural forces, uncovering the demonic entity within the boy’s shadow—a manifestation of Goki, an oni guardian sworn to Jiro’s protection.

When Senki enforces his claim, spiraling Kyoko into a fractured mental state, she is hospitalized and obsessively paints haunting oni imagery. Ryuichiro discerns these works anchor her soul to the Dark Demon World and shatters the paintings with a sledgehammer, severing the link and restoring her mind. This act repairs the family’s strained bonds, solidifying their acceptance of Jiro despite his otherworldly ties.

In the manga, Ryuichiro confronts adversaries like the Dark God School, wielding a shotgun with lethal precision to aid Jiro and allies. The OVA diminishes his role, stripping his combat agency. Both narratives converge as the family reunites, embracing Jiro’s dual heritage and cementing their enduring connection.