Kage-onna

Kage-onna (Japanese: 影女 or かげおんな, meaning "shadow woman") are shadow women which appear in abandoned buildings, run-down homes, and haunted houses in Japanese mythology.

Appearance
Kage onna are shadows of women which appear projected onto windows and doors when there is no one around to cast them. They appear late at night when the moon is bright, as the paper sliding doors and windows of traditional Japanese homes are particularly good at catching shadows in the moonlight. They usually take the form of a young lady, though occasionally, they appear as an old crone with a bell hanging from her neck.

Behavior
Kage-onna make no sound, nor do they interact with the house or its inhabitants, other than projecting an eerie atmosphere. Although they are not known to cause any harm to the residents of the house, the image of a person where there should be none is enough to startle the bravest person. If the door or window is opened to see who or what created the shadow, there is nothing to be seen. However, tradition says that a house where a kage-onna is seen is likely haunted, or will soon be haunted, by other yokai as well.

Origin
The moonlight frequently plays tricks on the eyes, causing people to see things in the darkness that aren’t really there, or casting eerie shadows on the ground and walls that don’t seem like they should really be there. Most of the time, this can be attributed to an overactive mind piecing together ghost stories and wandering thoughts and constructing some horrible figment of the imagination. Sometimes, however, a shadow is more than a shadow. Sometimes, it is a kage-onna.