The Anti-Spiral tells Nia that she is only a tool of the Anti-Spirals, but Nia keeps faith in Simon, who appears to rescue her. The Anti-Spiral is dumbfounded that they escaped the multiverse, and the Dai Gurren-dan unites into a gigantic Tengen Toppa Gurren Lagann. The Anti-Spiral attacks with a similar-looking mech named the Granzeboma, and Genome-- now with a complete body while they're in the spiralverse --explains that the Anti-Spirals want nothing more than to remove all hope from the Dai Gurren-dan.
Yoko identifies the Anti-Spiral's home world, and the Anti-Spiral tells them their history: they started out as spiral beings, and destroyed other spiral beings for power. Eventually they realized that their ways would destroy the universe and they became determined to keep spiral beings down and prevent them from doing the same thing. The Anti-Spiral demands to know whether Simon is as determined to protect the universe.
The Anti-Spiral answers itself by saying that the Dai Gurren-dan doesn't have that resolution and is simply drowning in power, and that's why they must be destroyed. The Dai Gurren-dan then thinks of the earth, which-- thanks to the incredible mix of spiral and anti-spiral power, appears before them. The Anti-Spiral reaches for it but is held back by the Dai Gurren-dan. Simon tells the Anti-Spiral that the tomorrow they want isn't the Anti-Spiral's, and that they'll reach for the tomorrow they do want-- and they'll protect the universe.
Lord Genome sacrifices himself in the battle, allowing the Gurren-Lagann to swallow his ganmen and take on incredible power. The Anti-Spirals don't understand the source of the power and Simon says they've evolved-- that a drill will inch them forward a tiny bit at a time. Simon charges forward and defeats the Anti-Spirals.
Everyone returns home and Nia and Simon get married almost immediately. However, because of the destruction of the Anti-Spirals, Nia is disappearing from the world-- she vanishes right after she and Simon kiss. Everyone worries about Simon but he knew it was coming. Gimmy suggests that he try to use spiral power to bring her back, but Yoko notes that Simon isn't (and doesn't want to be) god. Simon gives his core drill to Gimmy and leaves the government in Rossiu's hands, and becomes a wanderer, along with Boota.
Twenty years later, we see Rossiu and Leeron at a Galactic Spiral Peace conference, Yoko as principal at her school, Nakimu as a new recruit in the Grapal forces led by Gimmy and Darry, and Viral as a representative of Earth heading for deep space. That night, an old man gives a young boy advice on how to drill into a coconut, and the boy thanks the man, impressed. The man starts to ask who the boy thinks he is but then stops; the boy isn't paying attention anymore. He looks at the stars, and his companion-- Boota --tells him that that's where all his spiral friends are waiting.