After losing her husband, Reiko and her son Toshio settle in a village in the mountains. In this village, left behind by modern civilization, men and women seek each other out in the grass without any regard for the public's attention. Furthermore, learning that the custom of nighttime rape still exists, Toshio worries that his mother, Reiko, might be harmed by this... But one day, Toshio witnesses Reiko masturbating. Realizing that Reiko has no idea what to do with her body, Toshio begins to think of his mother as a woman...