When Shinhu Ki, the youngest prince of the Underworld, was tasked with guiding 30,000 spirits to the land of the dead, he figured it would be a breeze. Three years later, he’s barely made any progress until he meets Hajoon Yeon, who not only seems to be a lure for the spirits but is also full of yin, the source of Shinhu’s power. In exchange for helping Hajoon’s sick mother, the two enter into a contract where Shinhu can harvest that power anytime, anywhere he wants. And he wants a lot of it…