Mikami-Sensei

Mikami-Sensei is the vice homeroom (assistance) teacher of 9th Grade Class 3 at Yomiyama North Middle School. She is also the art teacher at the school and presides over the art club. She is revealed to be "another one" and the origin of the phenomenon that year. Originally, she drowned in 1996 when she was the homeroom teacher of Class 3-3.

Personality
She is shown to have a different personality when she's at school. She is described as a beautiful teacher and was dubbed the 'killer type'. Many students wanted her to be their homeroom teacher instead of Kubodera-Sensei.

Appearance
In the anime, she has long brown hair that is slightly wavy. In the manga, she has black hair and wears spectacles.

Plot
Although not immediatly obvious, Ms. Mikami and Reiko are the same person, and Kouichi just behaves differently around them whether they're at school or home.

In the original novel, the revelation of Ms. Mikami and Reiko's connection occurs at the climax of the story.