Futakuchi Onna

Futakuchi-Onna (lit. Two-Mouthed Woman) is a youkai woman with a second mouth on the back of her head. She is a member of the Youkai Castle trio alongside Tantanbou and Kamaitachi. Like her teammates, she first appeared in the Shonen Magazine story Youkai Castle. In the 1968 anime, her name is instead Ooguchi-Onna (lit. Large Mouth Woman).

(Source: GeGeGe no Kitarou Wiki)