The day before he begins attending high school, Ashiya Hanae becomes possessed by a strange fuzzy yokai and falls ill. Ashiya discovers the Mononokean, specialists in exorcising yokai, and meets the morose master Abeno Haruitsuki.

When Ashiya begins working at the Mononokean, the master Abeno tells him to pretend to not see any yokai other than the Mononokean's clients. However, the kind-hearted Ashiya is unable to keep his word, and the yokai won't leave him alone.

After making friends with his classmates Saga and Fushimi, Ashiya embarks on the high school life of his dreams. But before he has the chance to enjoy his new life, he's instructed to go to a temple alone to find and return a yokai's lost possession.

Ashiya asks to go with Abeno to a pharmacist in the Underworld. Though Abeno is reluctant to bring a human to the Underworld, he relents when the Mononokean suggests that Ashiya accompany him.

The Legislator, one of three influential figures of the Underworld, issues a rule that Abeno must bring Ashiya to see him. Unable to defy the Legislator's rules, Abeno is forced to pay a visit to him with Ashiya in town.

Abeno is hired by a certain yokai to find a human woman's missing ring and return it to her. Unable to find the ring on his own, he asks Ashiya to help. During their search, Ashiya demonstrates a surprising talent.