In Giha village, an underground town, Simon and Kamina live mundane lives with the constant threat of earthquakes. During an attempt to escape to the surface - something almost unheard of - Kamina and Simon bear witness to a gigantic wolf-faced Gunman, as it crashes through the ceiling into the middle of their subterranean home. Together with the Gunman's pursuer, a girl from the neighboring village, Yoko, the two young men find the key - a small Gunman buried deep in the ground, named Lagann by Kamina - to both defeating the massive intruder and leaving Giha Village.