One day, Mao was indulging in her usual masturbation session in the living room. Suddenly, her stepson Akihito returned home earlier than expected and caught her in the act. Flustered, she hurriedly tried to put her clothes back on, but accidentally forgot to put her panties back on. When discovered in that state, Akihito couldn't help but steal glances at his stepmother's bare hips, and soon found himself overcome with uncontrollable desire, forgetting all about their familial relationship.