In feudal Japan, the enigmatic Medicine Seller traverses the land hunting malevolent spirits known as 'mononoke.' Armed with the Exorcism Sword, he must first unravel the Form, Truth, and Reason of these entities before engaging in combat. His latest encounter takes him to an ancient inn where a pregnant woman, Shino, faces a perilous threat from the Zashiki Warashi spirits. Delving into psychological analysis and meticulous investigations, the Medicine Seller races against time to vanquish these deadly entities haunting the inn.