Sacchan, Boku wa.

Katagiri Kyosuke, who moved to Tokyo from the countryside to attend university, is in a long-distance relationship with "Sacchan." However, by chance, he ends up having a physical relationship with the married woman who lives near to his apartment. Thus begins a story surrounding an immoral love triangle… Kyosuke, who doesn't understand love, must choose between a girlfriend from his hometown or a married woman in the city. What is the fate of this destructive love affair?