In Japanese folklore rokurokubi are a type of yokai appearing as regular women but with the ability to extend their necks to extraordinary lengths (or sometimes completely detach them) so their heads can wander around without their bodies. Most rokurokubi just scare people rather than being dangerous, although this isn't always the case. It is believed they were once real women who were transformed into yokai as a result of either a curse or punishment.

🎨Backemono no e, ca. 1700.