Kou didn’t join. If you remember how pissed off he was at the asshole “Bask Om” when they still fired the big death beam even when Kou was still in range. There’s no way Kou is stupid enough to join a force led by that guy, or even continue fighting for the same people.
Also, I have another question. Universal century is easily one of my favorite eras. However, there’s one serious problem. THE ZEON NEVER WIN! Does anyone else want the Zeon to win?