Living underground in Giha Village, Simon and Kamina dream of a life on the surface. When their home is invaded from above, it is up to them to activate the mysterious mecha Lagann and save their village.

Now that they've made it to the surface, Simon and Kamina must join together with Yoko and her village to defeat the Beastmen pursuing them.

Nia true identity is revealed, as she flaunts her authority to get rid of another one of the Four Divine Generals, Adiane. The members of the Great Gurren Brigade are now suspicious of Nia and her true intentions, but she is only concerned about the depressed Simon. Adiane later returns to finish them all off, with Lordgenome's blessing.

Team Dai-Gurren are now on their way to Beastmen's capital city, Teppelin but there's a vast ocean in their way. The only way for them to get across is for the Dai-Gurren to be modified, so while they wait everyone goes to chill out at the beach. Once preparations are complete, the Great Gurren Brigade begins their cruise, but there's an ambush waiting for them.

At last, Team Dai-Gurren arrives at the outskirts of Teppelin, but before aiming to the city, they must face a combined full-scale attack of Cytomander and Guame's forces.