Princess Hours (2006)

Feisty, bubbly, and no-nonsense, Shin Chae Gyeong is an ordinary high school student. Until one day when she receives some unexpected news. Because of her grandfather's will, she must marry the unendurable Crown Prince Lee Shin who also happens to attend her high school. Chae Gyeong initially resists the proposal before reluctantly agreeing to marry him to help her debt-ridden family. As she struggles to adapt herself to royal life, learning proper manners and taking on the duties of palace life while dealing with a disagreeable husband, the Crown Prince's sentimental cousin and second-in-line to the throne, Prince Lee Yul, steps into her life. She feels like she can rely on Yul for help and guidance but still finds it difficult not to worry about her haughty, cold-hearted husband. To help bridge this gap, the senior members of the royal family take some special measures to get them to spend the night together.