Futakuchi-onna

In Japanese mythology and folklore, futakuchi-onna belongs to the same class of stories as rokurokubi, kuchisake-onna and yama-uba, women afflicted with a curse or supernatural disease that transforms them into yōkai.

In another story, the extra mouth is formed when a stingy woman was accidentally hit in the head by her husband's axe while he was 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.

Because she never ate a thing, and was still a hard worker, the old miser was extraordinarily thrilled with her, but on the other hand he began to wonder why his storage of rice was steadily decreasing.

To his horror, he saw his wife's hair part on the back of her head, her skull split wide open revealing a gaping mouth.