Yacha, meaning demon, is a historical drama set during the Joseon Dynasty. The monarchy is overrun with uncertainty, and the nation is left in the hands of precarious power-holders. Yacha's story centers around two brothers who find themselves amidst this political warfare. Baek Rok (Jo Dong Hyuk) is the intensely loyal, protective older brother who becomes the leader of the Black Swords, a secret political sect sworn to serve the king. Baek Gyeol (Seo Do Young of Spring Waltz) is the ambitious younger brother who takes the opposite side of the power struggle in order move out of his older brother's shadow. Their love for the same woman, Jung Yeon (Jun Hye Bin) puts their brotherly bond to the test.