Noppera-bō.

Noppera-bō (野箆坊, のっぺらぼう) looks human until the decisive instant. At first the figure may appear to be a traveler, a woman in distress, a vendor, or someone vaguely familiar. Only when approached or directly addressed does the face resolve into featureless skin, smooth and blank where eyes, nose, and mouth should be. The horror depends on that delay.

Unlike more elaborate monsters, the noppera-bō does not require claws, fangs, or strange anatomy. Its emptiness is enough. In illustrations and retellings the body remains ordinary, which makes the faceless reveal feel like a collapse inside the category of the human itself. The blank face is not just frightening because it is inhuman, but because it appears exactly where recognition should have been possible.

Noppera-bō mostly frighten rather than kill. Their favored action is the sudden revelation of blankness, often in a repeated or escalating sequence. A person sees one faceless figure, runs in panic, then meets a second apparent helper who asks what happened and erases its own face in the same way. This structure, later discussed as a recurrent-spooking motif, makes terror build through failed attempts to return to normal human contact.

Folklore often treats the faceless encounter as the trick of another shapeshifter, especially a mujina, kitsune, or tanuki. That ambiguity is part of the yōkai's identity. Noppera-bō can be read either as a creature in its own right or as the outward effect of shape-changing beings who choose the face as the point of attack.