Minako, a married woman living in an apartment complex with her husband, a researcher, is frustrated with her husband, who is so obsessed with his work that he neglects their lovemaking. While imagining the intense sex she has with her husband and masturbating to console herself, her eyes meet with a middle-aged man standing outside the open window. The man sincerely apologizes, saying he meant no harm, and Minako gradually opens Kokoro to him. The two, who were never meant to meet, end up in an affair that is so intense it leaves them covered in sweat after witnessing each other masturbating.