@ImperialAerosolKidFromEP: I feel like the only way they could've left Asia to the Japanese is if they hadn't attacked Pearl Harbour, Shanghai and the like anyway and drawn the Allies into the Pacific.
So if Japan didn't go to war with the Allies at all, it might not have had the kind of wartime shortages they suffered from, and had a stronger hold on Asia. Nevertheless, I don't think they could possibly have kept them longterm, since the general mistreatment of the Koreans by them would've probably created a rebellion against them, possibly leading to a similarly extremist government to what North Korea has now.
Tbh though, I feel like it was almost inevitable that the Japanese would've gone to war with the Allies eventually. There were too many colonies there at the time, and even if the war was limited in Asia, after it had ended in Europe I can imagine the Russians would still have gone into China eventually, leading to events not dissimilar to our Korean War, although perhaps with the Japanese on the South Korean side.
