Azusa, who has university entrance exams coming up, stays home alone while her family goes on a trip so she can attend summer cram school. Worried about her, her parents ask a relative's older sister to stay with her. That night, a severe thunderstorm causes a power outage, plunging them into darkness. With the air conditioner off, the room becomes stiflingly hot. Clinging to each other in fear of the thunder, the two gradually begin to sweat. Eventually, the scent of sweat begins to drive them wild...