The stories of the Kuchisake-onna, or Slit-Mouth Woman, is an old Japanese urban legend that has taken many forms as the story is retold from person to person and from generation to generation. The common theme of her story is that the Kuchisake-onna was attacked by someone, possibly her lover or a plastic surgeon or even herself, and her mouth was sliced open from ear to ear giving her a gastly grin.
It is said her spirit now roams the streets at night, wearing a surgical mask over her mouth. When she encounters a person, she will ask, "Am I pretty?" If the person answers yes, she removes her mask and asks, "How about now?" If the victim answers no, she either kills them or cuts their mouth to resemble hers. If the victim answers yes, she will follow them home, killing them at their door, because the word "kirei" (pretty) sounds like "kire" (to cut). In the 1970's it was said if you replied "You're average" your life was saved, however the saving response has continued to change with the years.