Yokai that started out life as a normal person. Such transformations are often triggered by strong desires or emotions. Some include:-

• Rokuro-kubi - A human that can elongate their necks to considerable distances. While they sleep their neck stretches and haunts the night by draining the life out of people or animals or by licking up lamp oil. Some humans afflicted with this curse may not be even aware they are doing this at night. Needless to say these Yokai aren't very successful in love.
• Futakuchi-onna - A futakuchi-onna is always a woman but can come about in three ways. She could have let her stepchild die of starvation, she could be the wife of a miser who neglects food, or she could be a rich woman whose husband's axe has cut the back of her head. All these causes exhibit the same symptoms. A mouth appears at the back of the woman's head and mumbles spiteful or threatening words to the women until it is fed, it may even resort to screaming. In time the hair of the woman moves to help feed the mouth.