Tengen Toppa Gurren Lagann: Giha Village is the home of Simon, a fourteen year-old digger who was orphaned when his parents were killed in an earthquake. Respected by the village elder as the best of the diggers, but ostracized by his peers, he discovers a special drill key deep in the ground, and recruited by an eccentric fellow orphan named Kamina into his group, the "Team Gurren". Kamina dreams of the surface world, which he visited as a child with his father, but had to return home because he was too weak to survive.
After a failed attempt at reaching the surface, Kamina is jailed by the elder and Simon resumes digging, only to discover "a big face" deep in his tunnel. As he excitedly fetches Kamina to show him the discovery, he is caught by the village elder, but Kamina's punishment is interrupted by the ceiling of Giha Village collapsing, as an enormous robot falls into the cavern. A girl named Yoko appears and tries to fight it with a large rifle, but cannot do much. Simon takes Kamina and Yoko to the "big face" he found earlier and discovers that the small drill key can be used to activate the small robot, which he uses to end up destroying the intruder, and effectively break through to the surface. On the surface, Simon and Kamina discover there are more large robots known as Gunmen, piloted by "Beastmen", that terrorize the surface dwellers during the day. Simon and Kamina help Yoko and her village destroy three more Gunmen and Kamina takes one for himself, naming it the Gurren. Eventually, Simon and Kamina decide that they will go on a journey to end the constant struggle between the Beastmen and humans, and are initially accompanied by Yoko and a mechanic from Yoko's village named Leeron, as they head out to find the Beastmen's Human Eradication Army headquarters, while dealing with various Beastmen warriors, including the vicious Viral.