Miroku Shikabane

She is the Japanese urban legend known as the "Kuchisake-onna" (slit mouthed woman.) She is also Koichi Sano's fiancé, and she has the goal of scaring him within a year, in order to get out of the marriage arrangement.

In chapter 45, she extends this year-long arrangement to be until Koichi's "heart stops." She also agrees to the marriage proposal, implying that she has fallen for Koichi.