Natsumi, a high school teacher who was troubled by her alcoholic husband, managed to get by by relying on her past love affair with her student Osawa. One day, she accidentally meets Osawa, who has now become a working adult. Osawa, who understood Natsumi's current situation, tells her, "You can rely on me anytime," and Natsumi's Kokoro wavers... Even though they are no longer teacher and student, infidelity remains. But the two of them can't stop it...!