Yua Mikami is a girl who is engaged and currently living with her future husband. One day, she attends a class reunion with her friends from the third grade. There, she meets her old boyfriend from three years ago, who is now a successful businessman. She is coerced by her ex-lover into having an affair. In the following days, he constantly finds ways to pursue her. Although she is being cheated on, her not-yet-married husband remains unaware and still holds feelings for her. Until one day, he decides to propose and receives a letter from the lover...