Adabana - Netorareta Hatsukoi no Hito wa Kekkon Shite Boku ni Dakasareru

After being turned down by his first love, Aya, Junpei is left no choice but to wish her happiness with her new husband. He resigns himself to never having her, but that all changes when her husband invites him over to their house… and asks Junpei to have sex with Aya.