My Little Bride (2004)

Boeun is an ordinary high school girl who worries about grades and has a crush on her school's baseball team ace, Jungwoo. One day, Boeun's grandfather orders her to marry Sangmin because of a pact he made with Sangmin's grandfather during the Korean War. Despite the grandchildren's opposition, they are forced to marry because of Boeun's grandfather's strong influence. She pretends that she doesn't have a husband and starts dating Jungwoo. Everything goes smoothly until Sangmin visits Boeun's school as a student teacher. There a teacher called Miss.Kim flirts with Sangmin and she later finds out that Sangmin and Boeun are married.