Yayoi is just another scientist working for Dr. Sanada in the real world, but in the parallel world, Yayoi was the former
pilot of Core Robot 1. She was injured while piloting it and Kazuki saved her. Her hair was burned in the accident, so she
has short hair for most of the series. Yayoi also becomes Kazuki's homeroom teacher at school. Yayoi always hangs out with
Kazuki and gang. She is even the homeroom teacher in Kauzki's and Mitsuki's perfect world. Yayoi has a thing for Kazuki, but
you have to keep in mind, Kazuki is nearly 10 years younger than her. I guess love knows no age.