In 18th-century Korea, Prince Yi San is a perfectionist haunted by his father's murder. He's set to inherit the throne once his cruel grandfather, the current king, passes away. Despite the emotional scars left by his father's death, Yi San aspires to be a benevolent ruler who reforms the kingdom's laws. At court, he encounters Sung Deok Im, a spirited and intelligent young woman. While Yi San falls in love and proposes she become his concubine, Sung Deok Im grapples with the restrictions and responsibilities that come with royal life. However, as their love deepens, she begins to see the potential to bring positive change to the troubled realm through their union.