In the summer of 202X, a crisis comes for the majority of demons who have been receiving human souls and filling their mana. As there are more devilish humans than demons, there is no need to seek help from demons even while selling their souls. In order to overcome this employment difficulty, demons are preparing to move to a 'mongma' that can absorb energy without human consent. It’s the same for Uffir, but it's not as easy as it sounds. In the end, a detective, Cheol-ho, appears in front of Uffir, who is trying to become a mongma by tricking him...