Miyuki Todou is a teacher at a high school who is engaged to Eiji Sanada, another teacher at the same school. While at work one day, Miyuki witnesses one of her fellow teachers having sex with a student named Misawa. Disturbed by what she saw, she contemplates telling Eiji. But Misawa tricks Miyuki into meeting him alone and making her keep quiet.
Based on Mesu Kyoushi - Injoku no Kyoushitsu the Eroge by Bishop