2006 90 il, sarang hal sigan

What happens to a love that is taboo and goes against society's morality? Hyun Ji Seok (Kang Ji Hwan) and Go Mi Yeon (Kim Ha Neul) are high school sweethearts. But they discover that they are cousins, and their love is forbidden by society's mores. So they go their separate ways. Years later in Seoul, Ji Seok is now a university professor and Mi Yeon is a scriptwriter.