For many years, Queen Inhyeon has struggled to produce a son as a way to protect the Royal Family. However, a fifth daughter is imparted upon her by the heavens after her only son dies in childbirth. Yi Yu is raised as a boy and must disguise herself as the family son called 'Yang Myung' in order to inherit and prevent the throne from being taken over by Queen Inhyeon's scheming rival and her two children as well as a rival competitor. Will Yi Yu be able to live the rest of her life as a man?