From CMX:
In a Tokyo playground, an innocent young boy is brutally slaughtered by a mysterious, scissor-wielding killer. Who could have done such a thing? The killing sparks a flurry of communications on the internet by frightened children from all over the city. Their speculation resurrects the myth of the dreaded "Slit-Mouth Woman," an urban legend that made the rounds some twenty years earlier about a mutilated woman who roams the earth, seeking revenge for her disfigurement. With its roots in Japanese mythology, the terror in this modern version of the story runs very deep indeed!

This manga is based on the 2007 Japanese horror film of the same name.