The Futakuchi-onna is, on the surface, an ordinary woman, but she conceals a second large mouth beneath the hair on the back of her head. That mouth works strands of hair like hands to drag food in and devour it greedily.
A woman who seems barely to eat yet consumes enormous amounts through a hidden mouth figures a suppressed hunger erupting where it cannot be seen. As another self concealed within one body, it carries the horror of duality.