The relationship between Yuto and Erika is suddenly getting closer!! What was originally a brother-sister relationship has developed into a romantic one!! However, their relationship is discovered by a teacher at the school, Ichinose Sayaka. Using this as a pretext, she blackmails (seduces) Yuto, and the two end up having a relationship. Yuto is elated, Erika is jealous of someone she doesn't know, and Sayaka falls in love with Yuto. The love triangle centered around Yuto reaches an unexpected conclusion...