In the arid realm of Sand Land, the vital river that once sustained life abruptly dries up, leaving the populace reliant on the tyrannical king's exorbitantly priced water bottles. Amid this parched coexistence of demons and humans, Sheriff Rao seeks the aid of the demon Beelzebub on a crucial mission to locate the elusive Phantom Lake, where mystical Water Finches reign. Initially hesitant, Beelzebub is swayed by a tempting offer and enlists the help of the seasoned demon Thief. Together, they embark on a quest to unveil the long-lost lake, driven by a shared desire to safeguard all beings, regardless of their species.