Rena Fukii travels to a hot spring resort with her son. To outsiders, they appear to be a loving mother and son, but in reality, they share a forbidden relationship. After arriving at the inn, they head to a private family bath. The son enters the tub first, while Rena follows shortly after. Male guests staying at the inn grow suspicious of their bond and begin secretly spying on them. As Rena apologizes to her waiting son in the bath, they exchange kisses, indulging in the sweet taboo of their incestuous affair. The men record the act without their knowledge, then later use the footage to blackmail Rena and take her by force. Though emotionally detached, Rena continues dining with her son, wanting to enjoy their trip. Suddenly, the men appear and summon her through the innkeeper, leaving her no choice but to accept her fate.