Just for you uneducated, here a quote from wikipedia:

"Kuchisake-onna (口裂け女, "Slit-Mouthed Woman") is a malevolent figure in Japanese urban legends and folklore. Described as the malicious spirit, or onryō, of a woman, she partially covers her face with a mask or other item and carries some sort of sharp object. She has been described as a contemporary yōkai.

According to popular legend, she asks potential victims if they think she is attractive. If they respond with "no", she will kill them with her weapon. If they say "yes", she will reveal that the corners of her mouth are slit from ear to ear, and she will then repeat her question. If the individual responds with "no", she will kill them with her weapon, and if they say "yes", she will cut the corners of their mouth in such a way that resembles her own disfigurement. Methods that can be used to survive an encounter with Kuchisake-onna include answering her question by describing her appearance as "average", or by distracting her with money or hard candies. "