Since her husband died in an accident, Natsuko has been raising her son Taichi on her own. Although her love for her husband has not cooled, her body is becoming more and more frustrated day by day. One day, Natsuko notices that Taichi is becoming a spitting image of her late husband. When she bumps into Taichi naked in the changing room, she discovers that even his penis is the same as hers, and finally takes the forbidden action...