"Those with blood on their blades don't cross the Lower Yangtze."

No So-ha, the sole heir to the reputedly invincible Nine Flow Swordsmanship, lives a low-profile life with three sources of income—fishing, ferrying customers through the Lower Yangtze, and as a contract hitman for victims of injustice. Despite trying to stay away from the conflicts among martial arts factions, he finds himself taking up the most dangerous job of all: escorting to safety a girl who holds the missing part of the Sun Gun Gyung, a medical treatise written for Emperor Qin Shi Huang that is the key to achieving immortality.