This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Rokurokubi (Japanese)
Rokurokubi is a type of Japanese apparition and 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 (nukekubi). The Rokurokubi appear in classical kaidan (spirit tales) and in y?kai works.
A beautiful and attractive woman by day, but at night the rokurokubi undergoes a metamorphosis. Her neck extends and she starts to hunt. Some rokurokubi are unaware of their condition and blame their nightly stalking of human prey on nightmares, while others are well aware of it.