|Book(s)||Konjaku Hyakki Shūi|
The Kage-Onna (影女 or かげおんな, Kage-Onna) is a yōkai and is considered harmless. She is basicly a shadow of a woman (hence her name) that appears either in particularly bright full-moon nights or in dark rooms, in the light falls out of a lit hallway or next room. Kage-onna is best illustrated in the book "Konjaku Hyakki Shuui" in 1780 by Sekien Toriyama.
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.
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.
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.
- Kage onna on Yokai.com