After Nobel Prize-winning scientist Klein is kidnapped and murdered, he transmigrates into a magical world beneath the Twin Moons: the Upper City floats in the sky, where mages hold life and death in their hands; the Lower City sinks into decay, where commoners’ lives are as worthless as weeds. He is saved by the kind scavenger Andre, only to witness Andre cut down in the street by the noble Leon, while Anna takes silver coins to buy a dress and turns to throw herself into the arms of power. Klein takes revenge with technology: he blows up the Stone Bridge and snipes Leon, and after killing a monster with a single shot, he draws the attention of the Imperial Monster Hunter Countess Violet. The two form a partnership. He builds an armed force of non-mages, develops firearms, factories, and tanks, and leads commoners to raise guns against mages for the first time. Within, the decadent royal family sends people to their deaths and doubles tax rates; beyond, a monster army opens blood-red eyes in the abyss. And when Violet is stripped of her title, deprived of her magic, and bound to the scaffold, Klein aims his gun at the Floating City, an age belonging to mortals is beginning with the first gunshot..
