The story is set beneath the surface of the great metropolis, below the district of Ogi-town in a realm of dreams that floats in a haze of purple lignite smoke. A network of roads stretches away underground, concealing bandits at every turn! An armored train snakes through the looming darkness: the steel-clad train Sokore 463 is equipped with a 75mm mountain gun that can blow a target to smithereens! In command is the mysterious girl Tanne. What awaits her and her comrades? From the winding alleys of Akegata (dawn) to the deep subterranean world of Kuragari (dark), a daring adventure unfolds!