The story set in a universe where South Korea is a constitutional monarchy. The Empress regnant, already in her thirties, is still unmarried and without an heir, which prompts the imperial court to look for a suitable Crown Prince. They encounter Lee Hoo, the son of the empress' uncle, and brings him into the palace where he begins to learn the life of a royal. However, another competitor arrives at the court: Lee Joon, the son of another uncle of the Empress. They compete for the title of Crown Prince via a trial of several tasks to determine the worthy future Emperor of the country.

Kang Poong-ho is a pest exterminator by day and a K-1/mixed martial arts fighter by night. He is a single father raising his 7-year-old son Kang San after the boy's mother, his first love Yoon So-yi, abandoned them to pursue her ambition of becoming a pianist. Despite life's trials, Poong-ho never loses his optimism and sense of humor. He meets and falls in love with Jeon Ha-ri, a bright and bubbly medical student from a wealthy family. An obstacle to their romance arises when they learn that Ha-ri's soon-to-be stepmother is none other So-yi and that it was Ha-ri's surgeon father Jeon Ki-suk who sponsored her piano studies abroad. As So-yi re-enters their lives, San is diagnosed with a brain tumor. Poong-ho is willing to go to any lengths to save his beloved son.

Costume designer Kong Hyun Soo fights against trials and hardships in order to succeed and find her happiness.