The original legend
According to the legend, she covers her mouth with a cloth mask, a fan, or a scarf. The woman will ask a potential victim "Am I pretty?" If they answer yes, she will remove her mask and ask them again in a girly voice. If the potential victim answers yes or screams, she will slash the victim from ear to ear so that the victim resembles her. If they answer no, she will walk away, only to follow her victim home and brutally murder them that night. Said reaction also occurs if you say no before she removes her mask. To avoid this fate, several people during the Edo period claimed that they gave her confusing answers like average and so-so or threw money or hard candy at her, buying themselves time to run away and lose her



Modern legend
According to the legend, she walks around wearing a surgical mask. The woman will ask a potential victim "Am I pretty?" If they answer no, she will kill them with a pair of scissors, which she carries in her pocket. If they answer yes, she will pull away the mask, revealing that her mouth is slit from ear to ear, and ask, "How about now?" If they answer no, she will cut her unfortunate victim in half. If the person answers yes, then she will slit his/her mouth so it resembles her mouth. It is impossible to run away from her, as she will simply reappear in front of the victim. When the legend reappeared in the 1970s, rumours of ways to escape also emerged. Some sources say she can also be confused by the victim answering her question with ambiguous answers, such as "You are average" or "So-so". Another method is to flip her questions towards her, such as asking her "Do you think I'm pretty?" Unsure of what to do, she will give a person enough time to escape while she is lost in thought. Another escape route is to tell her one has a previous engagement; she will pardon her manners and excuse herself. In some variations of the tale, she can be distracted by fruit or candies thrown at her which she will then pick up, thus giving the victim a chance to run.


Backstory
Kuchisake-Onna, as told commonly, was a beautiful, young woman that lived in a village of Japan. She would roam around the village, and ask the folks, "Am I pretty?", to which they would reply with an enthusiastic "yes". This made her very confident in herself, and as she was married to an intelligent samurai, she believed that she would be able to get away with an affair with a noble soldier. But her husband found out, and in anger, asked the soldier, "Why her? Why my lady rather than all the other women in the village?", to which he replied, "For she is the most beautiful in the village, I cannot pass up such an opportunity." The samurai adored his honesty and acknowledged that he had the right response and reason. The soldier was poor after all and had not had many positive things occur in his life. Although the soldier had proper intentions, the samurai's wife did not. She was the most beautiful woman of the village, and without that, she would be nothing. The samurai angrily took his sword upon her face, and slit her mouth from ear to ear, making her no longer beautiful. Soon after, she killed herself and was banished to an eternity of avenging her own pain.


(wish id heard about this folk law before Halloween.)