Kamina is jailed for trying to escape to the surface. Suddenly a mysterious women named Yoko comes from aboves to the underground village while fighting a giant robot. Simon helps fend off the robot with the help of his new "Gunmen" which he found while drilling around.

In the aftermath of the previous battle, Kamina, Simon, and Yoko proceed to forage for provisions. However, a chance encounter with a formidable Beastman, Viral, and his powerful Gunman forces the Gurren and the Lagann to combine to form a new Gunman.