Azusa and Yuu are teachers who work in the same workplace. They are a lesbian couple who keep their relationship a secret from their colleagues. After two years of living together, Yuu feels that sex with Azusa has become stale and is frustrated. She starts to feel thrilled and excited when a female student plays with her... Yuu thought that cheating between two girls wouldn't be considered cheating, but somewhere in Kokoro, she still feels guilty towards Azusa... However, Yuu is so immersed in her exciting daily life that she can't turn back.