Ji Hyung is engaged to a woman chosen by his family, but he in love with Seo Yeon. They’ve been dating for the past year with the understanding that their relationship would last only until Ji Hyung’s marriage. As the wedding date is set, the two break up. The heartbroken Seo Yeon starts to forget things, starting with the small and escalating to more important things that alarm her. As Seo Yeon’s memory loss becomes more severe, who will Ji Hyung choose to spend his life with?