Song-Joo (Kwon Sang-woo) and Jung-Seo (Choi Ji-woo) were destined to be together even before they were born. Both of their parents were close friends, they have almost grown up together since their childhood. They even looked alike as if they were twins. They even try not to be sick because one may worry the other. Song-Joo, being the only son of a multi-national cooperation, begins his business training and prepares himself to study abroad. Before Song-Joo’s departure, Jung-Seo and Song-Joo exchange necklaces as if they are exchanging parts of their souls. Time passes and Song-Joo returns from his studies to get back with Jung-Seo. But a tragic accident happens. Jung-Seo gets hit by Yoo-ri’s car and suffers amnesia. Jung-Seo doesn’t remember Song-Joo, who she loves the most and is not even able to identify his existence. She does not even remember her name.