Rokurokubi(轆轤首,rokurokubi?) which are related to Nure-onna are yōkai found in Japanese folklore. They look like normal human beings by day, but at night they gain the ability to stretch their necks to great lengths. They can also change their faces to those of terrifying Oni to better scare mortals.
In their daytime human forms, rokurokubi often live undetected and may even take mortal spouses. Many rokurokubi become so accustomed to such a life that they take great pains to keep their demonic forms secret. They are tricksters by nature, however, and the urge to frighten and spy on human beings is hard to resist. Some rokurokubi thus resort to revealing themselves only to drunkards, fools, the sleeping, or the blind in order to satisfy these urges. Other rokurokubi have no such compunctions and go about frightening mortals with abandon. A few, it is said, are not even aware of their true nature and consider themselves normal humans. This last group stretch their necks out while asleep in an involuntary action; upon waking up in the morning, they find they have weird dreams regarding seeing their surroundings in unnatural angles.
According to some tales, rokurokubi were once normal human beings but were transformed by karma for breaking various precepts of Buddhism. Often, these rokurokubi are truly sinister in nature, eating people or drinking their blood rather than merely frightening them. These demonicrokurokubi often have a favored prey, such as others who have broken Buddhist doctrine or human men.
In a folktale collected for his book, Kwaidan by Lafcadio Hearn, the nukekubi is misidentified as rokurokubi, an error that also appears in the Fighting Fantasy book, Sword of the Samurai, and in Stephen Dedman's novel The Art of Arrow-Cutting. The nukekubi is a similar but slightly different being from Japanese folklore belonging to the same overall class; instead of necks that stretch, the nukekubi have heads that completely detach. The book Even More Short & Shivery by Robert D. San Souci has a tale called Rokuro-kubi, but, again, the descriptions in the book are nukekubi, not rokurokubi.
Rokurokubi are in the film Pom Poko, during the "Operation Specter" scene.
Inuyasha, in the series of Inuyasha, fights with a "Spider Head", probably inspired by the rokurokubi.
In the anime/manga series Naruto Orochimaru uses a Technique called "Soft Physique Modification" where he can extend and bend different parts of his body which is very similar to Rokurokubi.
In the anime/manga series Rosario + Vampire one of the students is shown to be a rokurokubi.
In the manga Tokimeki Mononoke Jogakkou, the only teacher shown is named as a rokurokubi.
The Touhou series features a character named Sekibanki, who is stated to be a rokurokubi, but who has the ability to completely detach her head, making her more similar to a nukekubi (though her attacks use long, constricting strings of bullets that likely represent a rokurokubi neck). Her theme song's title and dialogue from one of the player characters additionally refer to her as a dullahan.