Tengen Toppa Gurren Lagann features Simon, a fourteen year old boy, who discovers an ancient mecha hidden deep in the recesses of the underground vault that is his hometown. After an enemy mecha crashes through the cieling of the vault, with beautiful marksman Yoko in hot pursuit, Simon and his bro, Kamina, decide to activate their mecha, newly christened Lagann, to fight off the invader. This catapults them into the hostile world outside the vault, where creatures called Beastmen use their mecha to rule with an iron fist, as they relentlessly war against the few existing human settlements. After a small victory against an attacking trio of Beastmen, Kamina decides to pilot his own mecha, built out of salvage from the attack. Naming it Gurren, the team then proceeds to take the fight to the Beastmen, not knowing that this will trigger a series of events that will put the fate of the entire world, nay, the entire Universe on their shoulders!