Let's Go, This is the Final Battle

A week after the moon was halted, Simon announces that Viral will sit in on strategy meetings. The beastman expects no forgiveness for the past, but wants it understood that humans are not the only ones with a stake in this world. Leeron's briefing assembles the bigger picture: the false moon was the disguised Cathedral Terra, spiral power flows from fighting spirit, and the Anti-Spirals began as spiral beings who concluded that unchecked spiral power would eventually destroy the universe. After winning their war, they hid their homeworld on a separate dimensional axis and built the eradication system that drove the spirals underground. Viral confirms that Lordgenome created the beastmen and propagated them through cloning, and Leeron's lecture on genetic diversity gets compressed, once the room's eyes glaze over, into the claim that love changes the universe. With an exploration system under construction aboard the Cathedral Terra, Simon commits to finding the enemy's home base.

Rossiu, meanwhile, travels back to Adai and returns the village's sacred book to the priest, admitting he never deciphered its ancient script and speculating that its author was pulling a prank. The two share a laugh over treasure turned junk, though Rossiu rejects the priest's suggestion that such reversals make people interesting. In the capital, Kinon shows Simon a farewell note tucked into the last page of Rossiu's reconstruction plan and recalls how he wept after Simon's trial, insisting he never seized power out of greed. Remembering how often Rossiu spoke of his birthplace, the two race to Adai aboard the Gurren Lagann.

Deep below the village, Rossiu reflects on a home that rationed life at fifty souls, on his conviction that the surface could hold everyone, and on the thousands he tried to sacrifice, a crime he intends to answer for. As he raises a gun to his head, the Cathedral Terra's systems detect a spiral metastasis reaction from the Gurren Lagann, which fires a beam that tears open a portal straight to him. Simon leaps from the cockpit and decks Rossiu across the face, telling him mistakes belong to everyone: getting hit for a failure is fair, but executing yourself over one is not. He admits Rossiu attempted what he himself never could, offers his hand, and says he still needs him, then corrects the record. Kinon needs him more, and she runs sobbing into Rossiu's arms.

Flying home with Kinon on his lap, Rossiu tells her that her weight is fine; he wants to know what one person's weight feels like. Later, a hologram of Lordgenome walks the crew through dimensional theory dense enough to lose even Leeron: Nia's ring is the beacon, and fighting spirit will fuel the warp to the Anti-Spiral homeworld. When Simon worries about leaving the planet exposed, Rossiu pushes him to go, pledging to manage in his absence.

The operation begins with the Cathedral Terra driving dimensional anchors into imaginary space and hauling the genuine moon back into orbit. As Simon says his goodbyes, Old Coco appears with an enormous Dai-Gurren-dan banner, which Simon and Viral carry into space and plant on the hull. In a new coat, Simon takes the bridge, rechristens the vessel the Chouginga Dai-Gurren, the Super Galactic Great Gurren, and declares that a united Dai-Gurren-dan has nothing to fear as the engines fire for what he names their final battle.

Rossiu attempts suicide in the depths of Adai, and Simon and Kinon stop him, with Simon forgiving him and naming him Earth's leader for the duration of the coming campaign.

The real moon is returned to orbit, the Cathedral Terra is renamed the Super Galaxy Dai-Gurren, and Team Dai-Gurren departs for Anti-Spiral space with Viral formally at the strategy table.

The Japanese title, Ikuzo Saigo no Tatakai da, matches the English broadcast title Let's Go, This is the Final Battle. The Japanese premiere fell on September 2, 2007, with the English airing on November 3, 2008, between Episode 22 and Episode 24.

The whole of Team Dai-Gurren debuts new outfits in the closing scenes, and the shot of Simon striding across the Super Galaxy Dai-Gurren deliberately echoes the prologue of Episode 1.