Hyun Ji-seok (Kang Ji-hwan), a university professor, and Go Mi-yeon (Kim Ha-neul), a scriptwriter, were high school sweethearts who discover that they are cousins. They break up, but find themselves attracted to one another once again when they meet in Seoul four years later. They decide to abandon everything and leave for America so that they can get married. However, Ji-seok's father finds out and runs in front of a truck, committing suicide, so that his son doesn't go. Although their visas have just been issued, Ji-seok cannot marry Mi-yeon knowing that their relationship was the cause of his father's death. He abandons Mi-yeon and marries Park Jeong-ran (Jung Hye-young), the daughter of his father's business rival, who is in love with him. They have a daughter, but their marriage is loveless. Mi-yeon goes on to marry another man, Kim Tae-hoon (Yoon Hee-seok).
Nine years later, when Ji-seok learns that he is terminally ill and has only 90 days left to live, he looks for Mi-yeon and asks her to spend the last few days of his life with him.
