One day, the high school student Okumura Kagerou was suddenly summoned to another world alongside his classmates. He received the class "Trap Master", a doomed one, which was looked down upon as a failure. While the heroes and swordsmen were celebrated, Kagerou was deemed useless, eventually being betrayed by his companions, who cast him aside in the deepest depths of a dungeon. There, he resigned himself to death when he found the demon lord, Aruel, sealed within a crystal. After learning the truth of this unjust world, Kagerou formed a contract with her and awakened his dormant power. The trap skills that were once riddled with restrictions were unleashed, evolving endlessly into the most powerful traps. This is the story of a forsaken, failed class rising up against injustice; an underdog becoming peerless fantasy!