Once inseparable companions Kwan Jin-Ho and Yun Zhen find themselves on different paths in a kingdom devastated by political intrigue and betrayal. Zhen, motivated by retaliation for his family's demise, joins a clandestine assassin guild, while Jin-Ho aspires to the noble life of a royal guard. Both must negotiate a maze of plots including the Crown Prince, covert guilds, and individual betrayals as their allegiances diverge. Their rivalry turns into a struggle for their souls as well as for survival as swords are pulled and hearts are split. Can brotherhood survive in a world where loyalties change, or will ambition and retaliation crush both?