The "Labyrinth" is a vast underground place where humans dwell in clusters known as "colonies." Over time, the surface has faded into obscurity—perhaps simply a fiction to those who have never witnessed its grandeur. A colony's members can take up a range of specialized tasks to ensure humanity's survival in the harsh circumstances of the subterranean. These include "Workers," who mine rare ore to fuel the colonies, and "Markers," who travel into the Labyrinth's unexpectedly lush environment to bring back information that helps with navigation. However, mankind is also threatened by beings known as "kaijuu," which range in size from a little child to an immense structure and are hostile to any human they see. Furthermore, huge enough kaijuu