Mizuki and her fiancé, Kazuya, are a happy couple preparing for marriage. However, Mizuki has a high libido and, secretly unsatisfied with Kazuya's performance, she resorts to masturbating in private. When Kazuya invites Michael—a Black man who helped him during his studies abroad—to stay at their home, their life as a trio begins. After accidentally catching a glimpse of Michael’s massive member, Mizuki becomes obsessed. Her curiosity quickly crosses the line as she seeks the physical satisfaction her fiancé could never provide.