In the purple smoke lies a faint dream, and in the town, rumors swirl like smoke. Now, facing the strangeness of the "mass disappearance" bewildering society, detective Soutarou confronts it! With no witnesses and unclear intentions, the identity of the "ominous tracks" that always appear in its footsteps... In search of clues, the detective delves into the underground realm of the town called "Kuragari." There, the encounter with the black iron armored train and its commander, Tanne, will significantly shake the fate of the detective!

This is a story that weaves together people and a town. A coal mining town crowded with small-scale excavators, commonly known as the "Hakoniwa." In this town that changes daily like a labyrinth, there's a girl named Kagari who runs a mapmaking business and a boy named Yuya who dreams of breaking free from the "Hakoniwa." Eventually, the two, along with the unique residents of the town, find themselves confronting a conspiracy that shakes the entire town. The fate of the” Hakoniwa" depends on Kagari's drawings on the map.