Rokurokubi is a yokai found in Japanese folklore. During the day they appear to be normal human beings, but at night they gain the ability to stretch their necks to great lengths like a snake.
Rokurokubis can also change his face to that of a hideous oni (Japanese ogre), to further scare mortals.
In their human form during the day, rokurokubi often live unnoticed and may even have mortal spouses. Many rokurokubi are so used to living normal lives that they go out of their way to keep their supernatural status a secret. But they are tricksters by nature, and they have a need to scare and spy on humans that is hard to resist. It is said that one can be a rokurokubi without knowing their own nature, believing they are really human beings, and only transform at night while sleeping unconsciously, remembering that when sleeping they saw the room or other places at a strange angle; thinking that it was a simple dream or an astral projection.
Often, the rokurokubi are truly sinister, going so far as to devour people or drink their blood, rather than just scaring them. They are similar to tanuki because of the characteristic of playing pranks on humans.