Byron Heiden, the eighth prince of the Lagon Kingdom, is ostracized for being an incompetent low-grade summoner. Consequently, he wastes his days fighting at a summoner gambling hall. However, as it turns out, Byron has been forced to hide his true powers from the public because he is the summoner of Russen the joker, a symbol of rebellion against the royal family. Despite knowing this, Taihan Heiden, the second prince, suddenly reappoints Byron as a successor of the throne and sets him on a mission to find the mysterious rebels that attacked the royal palace 11 years ago.