The red mask girl is a popular horror story, which I believe originated in Japan. However, it has also become popular in Korea. It has been added to the many stories used to scare school students.

There was once a woman who underwent plastic surgery. However, the surgery went horribly wrong. The doctor accidentally cut her lips up all the way to her ears (like the joker). She covers her face up with a red surgical mask and asks people if she is pretty or not. If they say “no,” she cuts their mouth to match hers. If they say “yes,” she will scream that they are lying and cut open their throat. Another version says that she will cut your mouth according to your blood type. If you are type A, she’ll only cut 1cm, type B would be a little longer. But if you are type O or AB, she’ll slit your mouth up to your ears.