It is the early Joseon period. Sanghyuk, the Fifth Prince of the Korean Empire has just turned 20. At the same time, the young and aloof West Marquis Hongbin, whom Sanghyuk remembers from his childhood, is returning to the capital for the first time in fifteen years. Hongbin shows up in the Imperial Palace as a prideful and conceited nobleman who no longer recognises the Fifth Prince. Unfazed, the young and playful Sanghyuk disguises himself as Hongbin's self-appointed right-hand man, willingly serving by the side of his stern new master without complaint. Meanwhile, Hongbin remains completely clueless about Sanghyuk's real identity - until the day the Fifth Prince succeeds the throne.