Ryohei begins living with his wife and her parents, but due to his poor health, he becomes unable to work and is treated coldly by both his wife and father-in-law. Amid this hardship, one person continues to show him kindness—his voluptuous and gentle mother-in-law, Erika. Initially, Ryohei feels nothing but gratitude for her warmth and compassion. However, as their bond gradually deepens, his rationality begins to crumble, giving way to forbidden desires he can no longer suppress.