START-419 A talkative high school teacher who missed her chance to get married is a complete pervert who enjoys exposing herself in class. When her students discover her hobby, she is forced to mate with them like a monkey, which makes her realize her female instincts. (Yui Mahiro - Yui Mahiro)

Ms. Yui is a tomboy who always wears sportswear and nags those dim-witted male students incessantly. The students laugh at her behind her back, saying things like, "She definitely doesn't have a boyfriend," "She's probably a virgin," and "She's completely missed her chance to get married." However, her true nature is that she has a higher sex drive than most people and is a complete pervert who likes to expose herself and masturbate when no one is around, either during or after school.