True Blue: Gaiden

Overview

Kanzaki Aoi and Kurusu Akito have broken their childhood relationship and are no longer together. Kaya, a girl who has been interested in Akito, decides to be with him instead. But, her efforts fail to make him forget about Aoi, who chose their P.E. teacher, Shudo, out of lust and has become the Shudo's mistress. During her attempts to gain Akito's affection, Kaya is blackmailed into having sexual acts with a guy who has been watching her. As she is forced to let him have his way with her, Kaya begins having obscene thoughts about Shudo. Little does she know that the teacher has been planning this all along...

Source: AniList