Three years ago, Kyosuke left home to attend university in Tokyo. Around that time, his father quit farming and started working in Sendai. Two years later, he remarried Natsumi. The stepmother and stepson only see each other twice a year, during Obon and New Year's. This summer, Kyosuke returns to the old wooden house, which still has no air conditioning. Reuniting with his stepmother Natsumi after a long time, he finds himself overwhelmed by the intense heatwave. Sweat pours from Natsumi's body, shaking Kyosuke's self-control. Gradually, he stops seeing her as just a mother figure and begins to desire her as a woman.