King Jinpyeong did not have any sons to name as a successor to his throne. Thus he named his eldest daughter, Princess Duk Man, to be his successor. The drama will be about the life of Princess Duk Man who was later known as Queen Seon Duk, the first Queen of Silla.

The Empress (Myung Se Bin) is in her early 30s, but she is still not married. Since, the 1st successor to the throne died, the royal family is in search for a new successor. Incidentally, they come to know of a young man who was in fact a son of the prince to a woman who left the Palace for her to be able to keep her pregnancy a secret. The young man's name was Lee Hoo (Se7en), more commonly known to his friends as Kang Hoo. Lee Hoo worked as a delivery boy at a Chinese restaurant, and was known for his 7-minute maximum delivery time. Lee Hoo had been brought up as more of a punk than a prince so his habits and his way of conversing were very different from the people of royal blood. Although he had never dreamt of living in the Palace, he one day finds himself immersing himself in its grandeur and improving himself to prove that he indeed deserves to be called the Successor to the throne.He soon finds out that not only will he be facing lessons to the path of royalty, and dilemmas of love and of stature, but he will also learn to compete for the position he had been, first and foremostly, called for.

Lee Se-na is the only daughter from a wealthy background. Because of her pampered upbringing, she believes that she can get anything she wants if she sets her heart to it. She meets Han Seung-Woo, a self-made diplomat, who is not-so-secretly in love with his childhood friend Yoon-su, currently in Japan with her fiance, Seung-Woo's colleague Jin-Hui. Se-na instantly falls in love with Seung-Woo, who asks her what she thinks the meaning of marriage is. In their subsequent marriage, their values are questioned as Se-na's complete trust in Seung-Woo shatters with the realization of Yoon-su's and Seung-Woo's relationship, and Seung-Woo's happiness in marriage shatters with Se-na's deepening mistrust and her own relationship with Jin-Hui.