The Kiheitai were formed to destroy everything. They're terrorists. Rebels. Criminals and now they're fighting to save Earth from total annihilation. The juxtaposition is perfect Gintama. Heavy action is balanced with heavy backstory. And of course, some classic Gintama banter between Takasugi and the other Joui 4 . Also Nobu Nobu, the former shogun who used to be a literal puppet for the bad guys, is running alongside Katsura declaring they're the national army. Katsura cuts him off and says they'll stick with being the rebel army. And Nobu Nobu smiles and says he'll join the rebel army to stand against the universe, perfect episode.