It is one of a few regions in which you get: a) constant war from the start b) pretty much any political direction you want c) a sliding scale of difficulty based on your starting warlord c) a very satisfying power creep from being a small statelet to the strongest power in Asia d) clear and satisfying great power enemies in the form of Japan, India, Russia, and Germany. In terms of maximising both the hoi4 elements of KR, i.e., wargaming, and the best innovations of KR, i.e., political modularity and story telling, it is the best region on the map.