Kare no Shiranai Himitsu wo Irete. The Animation

Two months into their new relationship, Yui and Naoya are still navigating the unfamiliar territory of being a couple. Their tentative romance takes a sudden turn when a passing stranger calls out to Yui by name, leaving her completely speechless. The man standing before them is someone from her past—the person who took her virginity. Driven by youthful curiosity about intimacy before she ever began dating Naoya, Yui had slept with him, a decision she believed was firmly buried in her history. However, that hidden chapter of her life refuses to stay in the past. Recognizing the opportunity for leverage, the man corners Yui with a chilling ultimatum: he will expose her previous sexual encounter to her unsuspecting boyfriend unless she complies with his demands. Faced with the devastating prospect of losing Naoya over a mistake made before their relationship even began, Yui is forced into a desperate position. Bound by blackmail and fear, she finds herself once again carrying a heavy secret, trapped in a compromising situation she cannot possibly share with the person she loves.