Hikari, a former company president's secretary who remarried a businessman, lives with her stepson, a grown man who has become a reclusive shut-in. Filled with maternal concern, she gently cares for him at home. One day, when she enters his room to encourage him, she notices her own panties are missing. Seeing her son frantically apologizing, Hikari forgives him kindly despite her confusion. But in that moment, overwhelmed by excitement, the son suddenly pins her down...!