Rokurokubiis a type of Japanese yōkai (apparition). They look almost completely like humans with some differences. There is a type whose neck stretches and another whose head detaches and flies around freely. The Rokurokubi appear in classical kaidan (spirit tales) and in yōkai works.
A yokai that looks like a human during the day and has a thin neck that stretches out at night. There are various theories, but it is said that the Rokurokubi could be seen as an out-of-body experience of a human being. In the Edo period, ghost stories were popular that prostitutes stretched their necks and licked the oil of lanterns when the guests were asleep.