Team Dai-Gurren managed to take control of the enemy fortress, but is still mourning the death of one of their own, especially Simon. After falling off a cliff, he notices a Gunman throw a capsule into a deep valley. Simon inspects it and finds he is able to open it with the same drill key he uses to pilot Lagann, and inside is a young human girl named Nia, but their introduction is cut short when an enemy Gunman appears.

After the Anti-Spirals' first attack and Nia's astonishing announcement, Simon looks desperately for her, while Rossiu finally completes his secret project.

Team Dai-Gurren struggles to escape from the ocean of despair created by the Anti-Spirals without success, until history repeats itself, as another irreplaceable member of the Team sacrifices himself to save the others.