Miki Koishikawa led a normal life before her parents decided to end their marriage. Despite her initial reluctance, she meets a handsome young man from another family, Yuu Matsuura. The situation is especially complicated because Miki's parents and Yuu's parents swap partners, and they all now live together in a grand estate. As Miki and Yuu grow closer, they must face their feelings, as well as outside forces seeking their attention, and any twists of fate that come their way.