Bichunmoo is set in 14th century Yuan Dynasty China, where the country is under Mongolian rule. The story revolves around the star-crossed lovers, Jinha and Sullie, the illegitimate daughter of a Mongolian commander, who find themselves caught in the middle of political intrigue.
After Sullie's mother passes away, her father, Taruga, takes her away and plans to marry her off to form an alliance with a powerful Chinese warlord. However, things take a dark turn when Jinha discovers that Taruga was responsible for the massacre of his entire family. Fueled by hatred, Jinha decides to master his family's secret martial arts, the Bichun Secret Art.
As Jinha becomes a target for many top pugilists who are also after the secret scroll, he receives unexpected help from Junkwang, a rich and powerful son of a Han lord. However, fate takes a cruel turn when Junkwang is revealed to be the person Sullie is forced to marry. When Junkwang learns about Jinha and Sullie's love, he plots to have Jinha killed.