You're Gonna Do It!!

Fresh off the bathhouse fiasco, the brigade faces Viral, who has come demanding a rematch with Kamina. Their duel is interrupted by the arrival of his reinforcements: Thymilph the Crasher, one of the Beastman Empire's Four Divine Generals, commanding an enormous mobile fortress called the Dai-Gunzan. Leeron immediately recognizes the fortress as the return point they have been hunting. Every voice but one urges retreat; Kamina instead squares up against the giant even as Thymilph shells Gurren Lagann at point-blank range and Yoko begs him to pull back.

When a shell mangles the mech's left leg, Kamina's sheer determination drives Gurren Lagann to repair itself. Unable to scale the fortress under his own power, he surfs the enemy's own explosions upward and delivers a burning kick to Enki on the Dai-Gunzan's deck. Three Gunmen launched at the noncombatants watching from afar are intercepted by an unfamiliar machine whose pilot proves to be Kittan, older brother of Kiyoh, Kinon, and Kiyal. Atop the fortress, Kamina announces himself to Thymilph, only for the Dai-Gunzan to snatch Gurren Lagann in its huge hands, batter it, and start wrenching its legs apart. Covering fire from yet another friendly Gunman, this one flown by Dayakka, saves the pair. Humans everywhere, it turns out, have been imitating Kamina and hijacking Gunmen of their own.

Yoko radios Kamina to hammer home that the whole group depends on him, but he still will not run. The breakthrough comes from an offhand remark: the fortress cannot be beaten while its legs keep churning. Simon asks for control, uses Gurren Lagann's agility to slip the barrage, and fires drills into the earth in a ring around the Dai-Gunzan, then collapses the ground beneath it. The toppled fortress is out of action, Viral swears to return the next day, and the day belongs to Simon. That night the team camps alongside its sudden small army of Gunman-riding allies. Leeron works on Gurren, whose leg damage reappeared the moment the two machines separated, while Dayakka explains that humanity now looks to Gurren Lagann as its banner of hope. After Kamina fires up the recruits with a speech, Leeron lays out a theory: since combination works by Lagann overriding Gurren's systems, Lagann might capture the Dai-Gunzan the same way, provided Simon's fighting spirit holds. Elsewhere, Yoko finds Kamina gazing at the moon. He tells her he fights so kids like Simon can live without fear; she answers that she respects that, then warns him never to repeat the day's recklessness, since only Simon's intervention kept him alive and the close call frightened her. She seems on the verge of saying something more when a distant mountain bursts into flame.

Thymilph and the Dai-Gunzan both debut, revealing the return point to be a moving fortress. Kittan arrives in his own stolen Gunman, and the episode also introduces Iraak Coega, Kidd Coega, Makken Jokin, Leyte Jokin, Zorthy Kanai, and the brothers Jorgun and Balinbow Bakusa, the growing core of what will become a full brigade. Simon pilots the combined Gurren Lagann to victory for the first time, and the plan to capture the Dai-Gunzan by fusing Lagann with it is conceived.

First broadcast in Japan on May 13, 2007, with the English airing on August 18, 2008. One animation quirk stands out: when Kamina exclaims about a mountain shooting at them, the mouth that moves belongs to Lagann's face rather than Gurren's, even though Simon pilots Lagann; the framing likely made Gurren's partially off-screen face impractical for showing dialogue.