I think that in post game there should be a gym filled with the first first boss but they won't attack the character because the one controlling the gym. You could possibly make it a tiny creature as the boss of that gym or a kuato as the leader of the gym.
Also may make kuato's a new enemy that could be used in possible dlc in the future to make it a link between both the syahata a bad day and the game that is after syahata s game.