Married for three years, Noa and Nobuo had a stable and harmonious relationship. One day, an unusual event occurs—Nobuo invites his subordinate, Kuroda, to their home. From then on, Kuroda is frequently invited over, and Noa begins to sense something off about her husband's behavior. Kuroda is young, attentive, and far more attractive than Nobuo. Gradually, Noa finds herself drawn to him, and eventually they become intimate. However, behind this affair lies an unexpected truth: seeking to break the monotony of married life, Nobuo had deliberately introduced Kuroda to bring new excitement into their relationship.