Hanae Ashiya's high school debut has been anything but smooth—he has spent the entire first week in the infirmary, and his baffling condition is only deteriorating. The source of his suffering is a mysterious, fuzzy creature that has latched onto him ever since he encountered it the day before classes started. As his health keeps declining and the creature grows larger, Hanae finds a flyer for an exorcist who banishes youkai. Desperate and with nothing left to lose, he calls the number and is directed to the Mononokean, a tea room that suddenly materializes next to the infirmary. A gloomy-sounding man, Haruitsuki Abeno, reluctantly assists Hanae but insists on payment afterward. To Hanae's dismay, he cannot afford the fee and must take a job at the Mononokean to work off his debt. To make matters worse, his new boss is actually one of his classmates. If Hanae ever hopes to clear his debt, he must work alongside Abeno to guide a variety of dangerous, strange, and interesting youkai back to the Underworld.