Saki married her boss, Kenzo, who granted her wish to continue working after marriage. Though she was living a fulfilling life, she still felt a barrier between her and her only son, Tsuyoshi. One day, Tsuyoshi happened to be on the train and saw her being molested. Tsuyoshi, who had secretly admired his stepmother, who was close to his age, began to feel desire for Saki, whose lewd behavior was a stark contrast to her usual pure appearance...
