なみは、バレー部のマネージャで同級生のたかしと付き合っている。前からなみが可愛いと目をつけていた体育教師の黒沢が、放課後二人きりでSEXをしているなみとたかしを目撃してしまう。たかし小さいチンポに満足できていないようだ。そして、まだ未開発のなみのマンコを見て犯したくなった黒沢はデカマラを見せつけ、無理やり挿入！それから黒沢に開発され続けデカマラに仰け反りイキまくり、彼氏がいるというのに寝取られにいくように―

Nami is the volleyball team's manager and is dating her classmate, Takashi. Kurosawa, the physical education teacher who had his eye on Nami for a while, witnesses her having sex alone after school. It seems Takashi's small penis isn't satisfying her. Seeing Nami's still-untouched pussy, Kurosawa, wanting to violate her, shows off his huge cock and forces himself inside her! From then on, Kurosawa continues to "develop" her, making her arch her back and orgasm repeatedly from his big cock, and even though she has a boyfriend, she seems to be willing to be cheated on—