The "Medicine Seller" is a lethal and enigmatic master of the occult who roams feudal Japan hunting malevolent spirits known as "mononoke" to destroy. Upon locating one of these entities, he cannot merely kill it; he must first uncover its Form, its Truth, and its Reason to wield the powerful Exorcism Sword and battle it. He initiates his peculiar exorcisms with rigorous psychological analysis and meticulous investigation—an exceedingly perilous phase, since he must confront and understand the mononoke before possessing the means to vanquish it. The Medicine Seller's path takes him to a traditional inn where Shino, a pregnant woman, has finally secured a place to rest. The proprietor has grudgingly assigned her the final empty room; yet, as she gets settled, it soon becomes evident that the room is overrun by a deadly group of mononoke, the Zashiki Warashi. Relying on his hunter's instinct, the Medicine Seller starts his inquiry to reveal the Form, the Truth, and the Reason before the Zashiki Warashi can claim another victim.