Futakuchi-onna are characterized as having two mouths, the regular one and another on the back of the head beneath the hair, where the woman's skull splits apart, forming lips, teeth, a tongue, creating an entirely-functional second mouth.

As if that weren't bad enough, the mouth begins the mumble spiteful and threatening things to itself, and demand food. If it is not fed, it will 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.