is Kōichi's aunt from Ritsuko's side and class 3-3 deputy homeroom teacher. Spoiler about Reiko!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 Kōichi addresses her as Reiko at home, and Ms. Mikami at school. She is revealed to be "another one" and the origin of the phenomena. Originally she died from drowning two years ago, when she was the homeroom teacher of class 3-3.