The Nopperabou is the mononoke at the center of the third story arc of the anime Mononoke, spanning episodes six and seven. This arc is also sometimes referred to as the Nopperabou or Faceless Ghost arc. The being is a supernatural entity, or mononoke, that draws heavily on the Japanese folklore figure of the noppera-bō, a yokai that appears as a normal human but lacks any facial features, possessing a smooth, blank surface where eyes, a nose, and a mouth should be. In the context of Mononoke, the Nopperabou is not a traditional monster acting on its own volition but a manifestation born from human emotion. It is described as a spirit that took form due to the conflicting emotions and deep psychological trauma of a young woman named Ochou. The Nopperabou serves as a direct reflection of Ochou's inner turmoil, confusion, and suffering. Its motivations are not those of a conscious being with its own desires; rather, it exists and behaves as a supernatural symptom of her unresolved pain. This makes it a more complex entity than a simple malevolent ghost. Within the story, the Nopperabou appears in a setting that may be partially or entirely constructed from Ochou's own mind, blurring the lines between reality and illusion. It often takes the form of a faceless humanoid, sometimes depicted wearing a Noh mask or a fox mask, and is referred to in some sources as the Man in the Fox Mask. The Medicine Seller must investigate this spirit to uncover its shape, truth, and reasoning in order to exorcise it. The process involves delving into Ochou's past and understanding the traumatic events that gave rise to the mononoke. The Nopperabou does not experience character development in a conventional sense, as it is a supernatural force rather than a person with agency. However, its role in the narrative evolves as the truth is revealed, and its purpose is fulfilled once it is understood and laid to rest. Key relationships for the Nopperabou are primarily with Ochou, the woman whose emotions created it, and the Medicine Seller, who confronts it. In terms of abilities, the Nopperabou can appear as a faceless being and has the power to manipulate perception and reality within its domain, trapping its victim in a cycle of fear and confusion. It is bound by the metaphysical rules of mononoke, meaning it can only be overcome when its form, truth, and regret are fully comprehended by the Medicine Seller.