A supernatural phenomenon where a human form takes on an unusual appearance at night, with the neck either stretching abnormally or flying away from the body. It is often associated with women and is said to manifest when they fall asleep. This appears frequently in classical ghost stories, essays, and picture scrolls, and can be broadly categorized into two types: those where the head detaches (nukekubi) and those where the neck stretches (rokurokubi). Some accounts interpret it as being caused by illness or karma, while many descriptions point out its creation for fascination with the bizarre.