A Noppera-bō is a demon from Japanese mythology. It is a faceless demon commonly mistaken for the Mujina. They are known to frighten people, but are harmless. At first, they appear as a family member or a friend of the victim. They will later make their face disappear, causing the victim to panic.
There are two stories which revolve around a Noppera-bō. The first is "The Noppera-bō and the Koi Pond", which is about a fisherman who goes fishing in the imperial Koi ponds, even though they are next to a graveyard. He is warned several times, but ignores the warnings. When at the pond, he meets a beautiful woman, who warns him to not go fishing. He ignores her, and to his horror, she wipes off her face. He runs home, to be comforted by his wife, who wipes off her face also. The second story is called "The Mujina of the Akasaka Road". This story is about a man traveling from Akasaka to Edo. He meets a beautiful woman, who is crying. He tries to comfort her, but she looks at him, and wipes all expression off her face. The man proceeds down the road until he meets a Soba vendor. The traveler relaxes, listening to the vendors tale, only to see him become a Noppera-bō at the end.