Shiina Yuna is a single mother raising her son (Kazuma) all by herself. Kazuma has a classmate named Ryuuta, who is a little twisted dude, and very smart for his age. He begins to like the Mother of his classmate and elaborates a plot to blackmail her, with the purpose of having sex with her. Shiina Yuna is a very strict Mom and a respected professional lady, but she finds herself bested and trapped in a situation she cannot escape from.
