As opposed to dealing with one of the urban legends that has already been on the show, I wanted to create something involving one of the few urban legends that the Winchesters have not faced in the 12-season run of Supernatural. I decided to go with Kuchisake-onna, otherwise known as the Slit-Mouth woman. The basic story is that she’s a Japanese ghost whose mouth was split open by her husband when he found out she was cheating on him.
Modern legends say that she walks around with a surgical mask on her face, asking passerby if they think she is pretty. Answer no, and she’ll stab you with scissors, killing you. Answer yes, and she’ll take the mask off, revealing her slashed face, and ask again. Answer no, and she’ll slice you in half. Say yes, and she’ll slash your face to look like hers. You may be able to trick her by giving a noncommittal answer such as, “so-so,” confusing her long enough for you to escape.
You can bet that the Winchesters would plan to distract her until they were able to burn her bones. And we all know that before Cas could give his planned answer of, “Beauty is a social construct designed by humans,” Dean would blurt out, “Hell no,” forcing them all to fight for their lives instead.