At her residence, Mei Onigami stumbles upon a peculiar spherical creature that incessantly utters 'chimi.' With the consent of her sisters, Mutsumi and Hazuki, they decide to accommodate the entity until its rightful owner materializes. However, a simple utterance of the word 'hell' triggers the spontaneous appearance of twelve more of these creatures. Initially unfazed, the trio soon witnesses these critters open a portal that beckons an emissary from the underworld. Enter Jabberwock the Eighth, a horned, fanged being draped in fur, dispatched to wreak havoc on earth by his superior. Struggling to adapt to human existence, Jabberwock finds refuge with the Onigami siblings, who also extend their hospitality to his 'Chimimoryo spirits'—the spherical demons heralding his arrival. Christened Jigoku-san by the Onigami trio, this infernal messenger faces the daunting task of world domination, but not before braving the mundane challenges of human life.