Futakuchi-onna (二口女, Futakuchi-onna), literally "woman with two mouths," refers to a yōkai from Japanese folklore.
Notably appearing in the Ehon hyaku monogatari, it takes the form of a woman with a second mouth at the back of her head, capable of ingesting food through it.
The story is said to take place in Shimōsa province, in a family where a man marries a woman in her second marriage. At the time of the second wife's arrival, the man already had a daughter from his previous wife.
However, the second wife only loved her own daughter of her own, neglecting her daughter-in-law, who eventually starved to death after 49 days.
Soon after, while the husband was cutting firewood, he accidentally injured his second wife on the back of the neck, leaving an open wound. With the passage of time, the wound became a mouth, with the skin forming the lips and the skull bones forming the teeth.
To ease the pain, food had to be inserted into the "mouth" of the wound, which seemed to soothe.
The "mouth" also made a sound, and when the husband approached it, he heard her say, "I killed my former wife's child out of negligence. Please forgive me. "
A similar story is that of a woman with pustules forming a human face on the back of her skull, who also demanded food, but this time because the person infected by the sore had allegedly done wrong.
However, both stories seem to have been written to teach people to be more human and empathetic.
The legend of the Futakuchi-onna was first compiled in the Ehon hyaku monogatari, but is not actually from the province of Shimōsa, and instead comes from the author.
Furthermore, even if the two-mouthed woman is merely a person suffering from an incongruous disease, Takehara Shunsensai's sketches instead show a woman with snake-like hair, which would make her a yōkai instead.
Many of the details of the story are also inconsistent.