راییکو میکامی

Kouichi's aunt from Ritsuko's side [Spoiler: and class 3-3 deputy homeroom teacher. She gives her nephew advice on how to make it through Yomiyama through a series of "rules". One of them is to separate the private life from school life, thus Kouichi addresses her as Reiko at home, and Ms. Mikami at school.]

[Spoiler: She is also revealed to be the extra/dead one. Reiko was murdered about a year and a half before the accidents started to happen.]