Oh! My God(2006)

Eun-joo falls for playboy Jung-hwan after he rescues her from drowning, and vows to make him her man. One thing leads to another, and they had a one night stand. Several years later, Jung-hwan is still living the high life while Eun-joo is working as a prosecutor. When they eventually cross paths, she reveals that he's the father of her twins, and tries to make him grow up and take responsibility.