Hanae Ashiya starts high school by accidentally picking up a clinging youkai that leaves him sick in the nurse's office all week. To get rid of it, he turns to Haruitsuki Abeno, the sullen keeper of a tea room called the Mononokean that doubles as a gateway to the Underworld. Abeno exorcises the spirit but saddles Ashiya with a million-yen debt, payable only in Underworld currency, so Ashiya is roped into helping handle the youkai who pass through the Mononokean.