In a Buddhist heaven where saints fight over turf in the clouds, Nio-maru searches for the younger sister torn from him in an aircraft accident back in the human world.

In her house, Mei Onigami discovers a strange round creature that only says "chimi." Her sisters, Mutsumi and Hazuki, agree to let the being stay with them until its owner comes to claim it. However, as soon as one of them utters the word "hell," more creatures show up until there are 12 in total. The sisters think nothing of this until the critters create a portal that summons an envoy from Hell. Jabberwock the Eighth, a horned and fanged man covered in fur, has come to unleash a living hell on earth under orders from his boss. However, when living in the human realm proves to be challenging, the Onigami sisters allow him to stay with them. They also take in his "Chimimoryo spirits"—the round demons that preceded his arrival. Called Jigoku-san by the Onigami sisters, this messenger from Hell has a lot of work cut out for him if he wants to take over the world. But before that, he will have to survive the everyday hells of human life.

A long time ago, Haruka Hoshinogawa made a wish with the town's old cherry blossom tree with her grandfather while receiving a present from him: a cherry blossom ribbon. As she grew up, she treasured the gift that was given to her while starting fifth grade in her school. One day, upon noting that the old cherry blossom tree is wilting, her grandfather decided to leave the shop to explore the world and let Haruka take care of the store in his absence. The next day while sleeping, her treasured ribbon sprouted a strange egg, revealing a Cocotama, a god born from an object that has been cherished with love and care. Haruka woke up and accidentally saw the Cocotama on the table, retreated to her Hiding Egg. As Haruka picked it up, it has changed into a mysterious key. Left with some questions, the Cocotama introduced herself as Ribbon, and Haruka learned about the existence of her kind and the mysteries behind the strange key she had. Ribbon realized that the key is actually the Key of Wonders and that Haruka was chosen by it to be the Legendary Contractor to the Cocotamas. Now, both of them try to run the shop and meet new Cocotama friends, while discovering the mysteries and powers behind the Key of Wonders.