Ayako, determined to hide her relationship with her only son Katsu from her husband, remained constantly on guard. However, Katsu, entering puberty, grew increasingly interested in sex and bolder in his actions. Though Ayako continued to exercise extreme caution to avoid detection, she gradually found her resolve wavering as she kept surrendering her body to Katsu. One day, the moment her husband left the house, Ayako secretly met Katsu again. The two exchanged passionate kisses, marking the beginning of a new chapter. Deep inside, Ayako sensed that her affair with Katsu could no longer remain hidden.