A noh mask, sometimes called as no-men (能面?) or omote (面?), is a traditional mask used in Noh drama, a traditional form a Japanese theater, Noh masks are considered to be supernatural in modern Japanese urban legends.
These urban legends may be influenced by the Noh mask's appearance, which can sometimes be considered unsettling. Noh masks are designed in such a way as to represent either a smiling face or a frowning face to the audience depending of the angle that the mask is held.
One urban legend concerning the noh mask states that, when kept within the house, the masks will absorb and feed upon the negative energy of their owners. The masks will continue to drain the energy from their owners until they've been completely consumed by the mask.