Kuchisake-onna - Japan

Kuchisake-onna, or the Slit-Mouthed Woman, is a woman whose husband slit her mouth open on either side and returned as a spirit. She appears to children who are alone, wearing a surgical mask and asks "Am I pretty?" If they say no, she kills them. If they say yes, she removes her mask, revealing her mouth and asks again. If they say no, she cuts them in half at the waist. If they say yes, she cuts their mouths to match hers. You can't run from her either, as she'll simply reappear in front of you. Where this gets legitimately creepy is that there were actually reports of sighting in 1979 in Japan, and in South Korea in 2004. Some schools in Japan even had children escorted home by teachers.