In a future world known as Sand Land, the one river that supplied the entire world had suddenly stopped, and the only source of water is from the greedy king's overpriced water bottles. Demons and humans live together in a world of drought, until Sheriff Rao confronts Beelzebub in need of a demon on a quest to find the Phantom Lake, a river on which birds called Water Finches supply themselves. Though reluctant at first, Beelzebub goes along (thanks to a good bribe) and brings an older demon, Thief, with him to find the lake for the good of all creatures, whether demon or human.