Childhood friends Baek Dong Soo and Yeo Woon are both prodigies in combat. But while Baek Dong Soo became the top swordsman in the land, Yeo Woon would go on to serve a group of clandestine assassins whose aim is to overthrow the throne.

Childhood friends Baek Dong Soo and Yeo Woon are both prodigies in combat. But they follow divergent paths. Baek Dong Soo supports the King and became the top swordsman in the land, Yeo Woon elects to join a group of clandestine assassins called the Black Ninjas whose aim is to overthrow the throne.—netflix