Background
The Slit-Mouthed Woman as seen in the film Carved.
The Slit-Mouthed Woman (or Kuchisake-onna) is a prominent Japanese urban legend. Rumors of alleged sightings of the Slit-Mouthed Woman began spreading around in 1979 around the Nagasaki Prefecture, causing panic in many Japanese towns. Reports also indicate that children were dismissed from school in groups escorted by a teacher for safety, and of police officers increasing their patrols.
The Legend
The legend has it that a beautiful woman lived in Japan years ago. But one day, her husband found out that she had fell in love with another man. So he came home and slit her mouth ear to ear, and she died from the blood loss. Her husband said, "Who will think you're beautiful now?" She goes and asks a child, "Am I beautiful?" If the child says no, she will kill him or her. If the child says yes, then she will take down her mask and ask again, "Am I beautiful now?" If the child says yes, she will kill them. If the child says no then the child will get killed. Some kids found a way do confuse her by saying "so-so"; it will confuse her long enough for them to run away.
The Slit-Mouthed woman later returned as a vengeful spirit wearing a surgical mask (which isn't uncommon in Japan, as many Japanese people wear surgical masks to prevent other people from being infected by their colds and sickness). She will approach a child and ask them, "Am I pretty?" If the child answers "Yes", she will take off her surgical mask, revealing her Glasgow smile and ask, "How about now?" If the child changes their answer to "No", she cuts them in half. If the child sticks to their answer of "Yes", she will slit their mouth just like hers. Running away from her will not work, as she will simply reappear in front of the victim. The only sure way of escaping The Slit-Mouthed Woman alive and unharmed is to give her an ambigious answer such as "You are average" or "So-so" which will confuse her and give the person enough time to escape. If the victim throws sweets and candies at her, she would be distracted and try to eat them. This gives the victim enough time to run. The slit-mouthed woman would also have a privilege to appear in front of the victim. Another way is to say if the child is pretty. She will get confused and walk away and kiss the victim.
Media
The Slit-Mouthed Woman urban legend has appeared prominently in two Japanese films: Carved (2007) and it's prequel Carved 2: The Scissors Massacre (2008).