In an unusual arrangement, Miroku-san, also known as the slit-mouth woman, is set to wed high school student Kouichi as part of a tradition in his family dedicated to preserving superstitions. But there's more to Kouichi's willingness beyond tradition. Miroku, preferring to rely on her own abilities, strikes a deal with Kouichi. They agree to a one-year trial marriage where, if she can frighten him within that time, the engagement will be called off.