Sasuke and Naruto are somehow stripped of their current absurd power levels. This would happen due to the end of the cycle in which the sons of kaguya reincarnate continuously. Despite his roll in saving the world, the united shinobi alliance wishes sasuke to pay for his crimes, which he is not willing to do, and thus becomes rogue once more, albeit he isn't hellbent evil. Sasuke then becomes a much more morally grey antagonist.