Mob, Reigen, Dimple, and the newest member of the Spirits and Such Consultation Office staff, Serizawa, take a trip up to a secluded hot spring called Ibogami Hot Springs in Zebra Prefecture. Reigen happened to get a request from the matron there to discover the truth behind the strange rumors going around there and save the inn. Ritsu and Teru also join in on this trip and the six of them head out on this super relaxing trip to the hot spring. But on their way there, Reigen and Serizawa start nodding off on the train and somehow get sucked into an eerie parallel world...

(Source: Crunchyroll)