Kuchisake-onna

A young woman who lived hundreds of years ago and was the wife or concubine of a samurai. She was very beautiful but also very vain, and she was discovered to have been cheating on her husband. The samurai, extremely jealous and feeling cuckolded, attacked her and slit her mouth from ear to ear, screaming "Who will think you’re beautiful now?

That woman roams around during foggy evenings, with her face covered by a surgical mask, which would not be especially unusual, as people with colds often wear masks for the sake of others in Japan. When she encounters someone, primarily children or college students, she will shyly ask, "Am I beautiful?" ("Watashi kirei?").
If the person answers yes, she will take off her mask and say, "Even like this?"
At this point, if the victim answers "No," she will slay them with a pair of huge scissors.
If the victim tells her she is pretty a second time, she follows the victim home and slays them in their own doorway. This is because  the word "kirei" , Japanese for ‘pretty,’ is a near homophone of "kire", the imperative form of "to cut".
If the victim answers "You’re average", they are saved.
Also, the answer "so-so," causes the Kuchisake-onna to think about what to do, and her victim can escape while she is in thought. One way to escape is to present the Kuchisake-onna with amber, hard candy. Another is to say "pomade" three times (in some versions, six times). This will make her either falter and turn or run away. If the victim has pomade, they can write with it behind her back to keep her from following. The reason is that this reminds her of either the dentist’s or (plastic) surgery smells, or that her boyfriend used it.