|Book(s)||Ehon Hyaku Monogatari|
In Japanese mythology and folklore, the futakuchi-onna belongs to the same class of stories as the rokurokubi, kuchisake-onna and the yama-uba, women afflicted with a curse or supernatural disease that transforms them into yōkai. The supernatural nature of the women in these stories is usually concealed until the last minute, when the true self is revealed.
The origin of a futakuchi-onna's second mouth is often linked to how little a woman eats. In many stories, the soon-to-be futakuchi-onna is a wife of a miser and rarely eats. To counteract this, a second mouth mysteriously appears on the back of the woman's head. The second mouth often mumbles spiteful and threatening things to the woman and demands food. If it is not fed, it can screech obscenely and cause the woman tremendous pain. Eventually, the woman's hair begins to move like a pair of serpents, allowing the mouth to help itself to the woman's meals. While no food passes through her normal lips, the mouth in the back of her head consumes twice what the other one would. In another story, the extra mouth is formed when a stingy woman is accidentally hit in the head by her husband's axe while he is chopping wood, and the wound never heals. Other stories have the woman as a mother who lets her stepchild die of starvation while keeping her own offspring well fed; presumably, the spirit of the neglected child lodges itself in the stepmother's or the surviving daughter's body to exact revenge.
Families which notice their food stocks are shrinking at an alarming rate while the women in their houses rarely eat a bite may be the victims of a futakuchi onna infestation. Futakuchi onna appear just as a regular women until their terrible secret is revealed: in the back of their skulls, buried beneath of long, thick hair, is a second mouth, with large, fat lips, and full of teeth. This second mouth is ravenous, and uses long strands of hair like tentacles to gorge itself on any food it can find.
In a small rural village in Fukushima there lived a stingy miser who, because he could not bear the thought of paying for food to support a family, lived entirely by himself. One day he met a woman who did not eat anything at all, and he immediately took her for his wife. Because she never ate a thing, and was still a hard worker, the miser was thrilled with her. However, his stores of rice were steadily decreasing, and he could not figure why, for he never saw his wife eat. One day the miser pretended to leave for work, but instead stayed behind to spy on his new wife. She untied her hair, revealing a second mouth on the back of her head, complete with ghastly lips and teeth. Her hair reached out with tentacle-like stalks and began to scoop rice balls into the second mouth, with cooed out with pleasure in a vulgar, raspy voice.
The miser was horrified and resolved to divorce his wife. However, she learned of his plan before he could act on it, and she trapped him in a bathtub and carried it off into the mountains. The miser managed to escape, and hid in a heavily-scented lily marsh, where the futakuchi-onna could not find him.
Another story tells of a wicked stepmother who always gave plenty of food to her own daughter, but never enough to her stepdaughter. Gradually the stepdaughter grew sicker and sicker, until she starved to death. Forty-nine days later, the wicked stepmother was afflicted with a terrible headache. The back of her head split open, and lips, teeth, and a tongue formed. The new mouth ached with debilitating pain until it was fed, and it shrieked in the voice of the dead stepdaughter. From then on the stepmother always had to feed both of her mouths, and always felt the hunger pangs of the stepdaughter she murdered.
- The long-running anime series Gegege no Kitarō often features Futakuchi-onna as an antagonist to Kitaro. Her skin is a pale white with raven black hair which can form snake-like ropes that stretch out and snare victims, often to pull them towards her horrifically large mouth on the back of her head which has sharp teeth. She is also known to work with other Yōkai antagonists Kamaitachi and Tantanbō.
- The 2005 movie "The Great Yokai War" briefly features a futakuchi-onna.
- In the video game The Last Blade, the character Akari Ichijou uses various attacks that involve yōkai. One of them is a special move that summons "a hundred yōkai" that parade across the screen in a procession. A futakuchi-onna is featured in this procession.
- Samurai Sentai Shinkenger and Power Rangers Samurai villain Tayu Usukawa is themed after the Futakuchi-onna.
- The television horror anthology series Masters of Horror featured a creature similar to a futakuchi-onna as a main character in the episode, Imprint.
- The Pokémon Mawile is based on the futakuchi-onna.
- In the video game Skullgirls, Filia bears a resemblance to the futakuchi-onna, with Samson, a parasite taking the place of her hair, acting as the second mouth.
- In the video game Ragnarok Online, the Miyabi Doll creature is based on futakuchi-onna.
- In the animated series Adventure Time, the "Fruit Witches" appear to be based on the futakuchi-onna.
- The comic Eerie Cuties featured a Futakuchi-onna as a history teacher.
- The adult-oriented strategy game Sengoku Rance features a female ninja character named "Orime" who is based off the Futakuchi-onna.