The moral of most Japanese urban legends seem to consist of "don't go anywhere by yourself. Ever." The story of the Kuchisake-Onna, or "Split Mouth Woman" is no different. Except that you are doubly unfortunate if you happen to be a child (We assume your legs are stubby and slow and we can thusly outrun you).
If you happen to be a snotty pubescent walking alone one day, you might consider taking a different route if you are suddenly approached by a female figure in a trench-coat. Now, before you assume that this will be a harmless display of kibbles and bits, rest assured: You will be shown something. Unfortunately, it will not be the coveted boobies.
The Kuchisake-Onna will appear as a tall woman in a trench-coat with long, black hair. Her most telling feature is the surgical mask covering the bottom half of her face.
She will approach you and ask you a question: "Am I beautiful?"
If you reply, "No!" Your troubles are over. Mainly because she will produce a comically oversized pair of scissors and remove your head. Ah! You're thinking, So I'll answer "yes!" In which case she will remove her mask to reveal her grotesquely mutilated face, her smile sliced from ear to ear. "Am I still beautiful?" She will ask again.
If you have some kind of twisted Joker fetish and reply, "yes", she will take the aforementioned scissors, chase you down, and slice you in half. If you reply "no", she'll do it anyway. Some people just can't be satisfied.
If you don't fancy a haircut with too much off the top, your best bet is a neutral reply, such as "You're so-so", or "average". This will confuse the Split Mouth Woman, giving you just enough time to run like all the hounds of hell are at your heels (or in this case, a crazy bitch with a giant pair of scissors)
Read more: 8 Scary Japanese Urban Legends | Cracked.com link