Nanami is married to a reserved man, but finds herself involved with her husband's complete opposite—his carefree, womanizing younger brother. Though she never harbored any feelings for him and initially resents the arrangement, she reluctantly agrees to cooperate when her husband asks her to try conceiving a child with his brother due to fertility concerns. Though the situation is far from what she desires, Nanami clings to the hope of becoming pregnant. However, as they continue their physical relationship, the brother grows increasingly bold and familiar with her. Despite her attempts to maintain boundaries, he justifies his advances by claiming it's "at my brother's request" or "for the sake of making a baby," repeatedly pressing himself on her. How long can Nanami endure this? The unfolding tension and evolution of their forbidden relationship lie at the heart of this intense incest and NTR drama.