Rokurokubi are demons 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.