A Futakuchi-onna is a legendary Japanese monster, or yokai. The name Futakuchi-onna means "two-mouthed woman," and as the name suggests, this type of monster has two functional mouths. The second mouth is in the back of her head. Futakuchi-onna appear throughout Japanese folklore, in which the second mouth usually is the result of a curse or some other supernatural cause. In this type of story, the woman's true nature is often hidden for much of the story before finally being revealed.
The second mouth of a Futakuchi-onna must eat, often much more than a regular mouth. If it is not fed, it might begin to mumble and threaten the woman, and it might experience pain and begin screaming. The hair of this monster is sometimes said to become tentacle-like, picking up the woman's food from her plate and feeding the second mouth.
In many stories, a woman becomes a Futakuchi-onna after letting her stepchild starve to death; in such cases, the dead child's spirit puts the curse into effect and might even reside in the woman's body. In other tales, these women are the wives of misers, and they become cursed as a result of their husbands' stinginess. In one story, a woman becomes a Futakuchi-onna after her husband strikes the back of her head with an axe. Instead of healing, the wound becomes a second mouth that must be fed.
One of the most well-known Futakuchi-onna stories tells of a man who chose his bride because she never ate a thing. As a miser, he could not bear the thought of having to feed another person, so the fact that his wife never ate was a huge attraction. He soon noticed, however, that his stores of rice were mysteriously being depleted. When he spied on his wife one day to see what was going on, he discovered that she was a Futakuchi-onna. He saw a gaping mouth open in the back of her head, and when she unbound her hair, the hair shoveled huge quantities of rice into her second mouth.