Zein, a 19 year old student was on his way home when he encounters a demon named Peach. She claimed to be the 13th member of the 13 Demon Representatives, who were assigned to purge Monsters that escaped abyss currenty roaming the earth. For Demons to remain on earth for a prolonged period, they require a contract. An agreement of companionship with penalty of Eternal suffering at the river of flames if not fulfilled. Will they be able to combat the supernatural,while abiding to a contract?