>>54098566FPBP. More or less explains it. Kitakami is a region, though it may not be prevalent enough to warrant a full Pokemon League in the same way that many of the other regions do. Over the years, we have witnessed some deviations from the typical League system: Kanto and Johto sharing an Elite Four and Champion, Alola having Trials and Trial Captains as predecessors to formal Pokemon Gyms as well as the beginnings of an all new Pokemon League, Galar hosting a Semifinals Tournament amongst applicable challengers and Gym Leaders instead of using an Elite Four, and finally, Paldea's "Top Champion" and "Champion-level Trainers".
Kitakami might have its own local, traditional organization within it over a formal, spanning League.
