The early 14th century. Prince Chhungsun, heir to the Korean throne. He is the son of the famous ruler of Goryeo Chungnyeol and a Mongol princess, daughter of Kublai Khan. From an early age, the boy was taught calligraphy and the martial arts, the etiquette of both kingdoms, and various traditions. But it happened that there are only two people in the world whose opinions matter to Prince Chhungsun: his personal bodyguard and distant relative Rin, and also the daughter of the wealthiest man in Goryeo, In-san.