Married for three years, Yui's husband has been busy with work, causing emotional distance between them. At a high school reunion, she reconnects with her former boyfriend, reigniting long-suppressed feelings. With growing sexual frustration and emotional emptiness, their reunion gradually turns into a passionate affair. Despite trying to resist, her heart gives in to desire. Seeking intimacy and connection, the two embark on a hot springs trip, where their emotions intensify and their forbidden relationship deepens.