The story takes place during the Yuan Dynasty. The legendary assassin Zixialang (played by Shin Hyun-jun) stands on the roof of a noble mansion, looking at the woman who has haunted him all his life, with mixed feelings in his heart. Many years ago, Liu Zhenhe, a descendant of the Goryeo people, was wandering around and practicing martial arts. He accidentally rescued Shirley, the daughter of a Mongolian general, in the jungle. The boy and girl who were childhood friends became friends, and their ten years of companionship made them deeply attached to each other. However, fate played tricks on people, and Zhenhe had to part with Shirley (played by Kim Hee-sun). Shirley was influenced by her father and was about to marry Namgoong Jun-gwang, the only son of the Namgoong family. Zhenhe, who had learned peerless martial arts, learned about his life experience. He came back to Shirley after many twists and turns, but his fate could not be changed. Zhenhe, who became Zixialang, was incompatible with the pro-Yuan faction Namgoong family, and he inevitably drifted away from Shirley, who he always cherished... This film is adapted from the original work of Korean cartoonist Kim Hye-rin.