Mei Onigami encounters a peculiar round creature that keeps repeating "chimi." Along with her sisters Mutsumi and Hazuki, they decide to look after it until someone claims it. When the word "hell" is accidentally uttered, eleven more of these beings appear, bringing the total to twelve. Initially unconcerned, the sisters' peace is broken when a portal opens and summons Jabberwock the Eighth, a demonic emissary from Hell. Covered in fur with horns and fangs, he arrives on Earth intending to unleash chaos under his superior's orders. However, finding human existence difficult, the sisters allow him to remain, along with the round Chimimoryo spirits. Nicknamed Jigoku-san by the family, this envoy from Hell must first manage the challenges of everyday human life before he can attempt to take over the world.
