In order to take the fight to the Beastmen, Team Gurren sets out to strike a possible Gunmen rallying point. Along the way, they encounter the eccentric Black Siblings, as well as the prospects of having to defeat a multi-faced enemy.

On their way to the Gunmen rallying point, Team Gurren decides to take a break at a hot springs getaway they find in the middle of nowhere, only to discover not everything is as it seems.