When stumbling upon a mysterious underground expanse in his own backyard, Ezoe Kazuhiko unwittingly triggers the Dungeon System, kickstarting a race against time. With 666 dungeons looming and a decade to vanquish them all, failure means catastrophic obliteration. Guided by the enigmatic Akane, Ezoe embarks on a quest to assemble allies and establish Dungeon Busters Inc., a bold venture aimed at conquering the impending doom. As nations mobilize in response to the proliferating dungeons worldwide, the stage is set for a gritty, high-stakes adventure into the depths of these perilous labyrinths.