Hannya (serpent): a mask used a woman who has become demonic because of jealousy and lust; generally demonic female jealousy was represented using serpent imagery . The name Hannya literally means "half demon" and compared to the next mask, Shinja (true serpent) you can still see traces of the woman's humanity in the expression around the eyes. Notice how stylized the lines of this mask are compared to the Hannya mask below.

This image is from a performance of Aoi no Ue. Note the triangle pattern on the head band and upper robe: it represents serpent scales. The red split pants (hakama) are quite long and trail out behind the actor, reinforcing the impression of a serpent.