I remember learning in school a few years ago that the Japanese were really massively punching above their weight during WWII, especially when fighting against the United States. This was because Imperial Japan had an even smaller economy than Fascist Italy at the time, which is notably a country we largely tend to think of as being the weakest link of the Axis powers. So in a world where the Japanese had been highly successful in realizing their wartime ambitions, what were they intending to do afterwards with and in their newly acquired and subjugated imperial possessions? Would they have carried out an Imperial Japanese equivalent to the Nazis’ ‘Generalplan Ost’, and if so, what exactly were their intents and plans?
I've previously answered a question similar to this here, along with valuable contributions by /u/StarWarsNerd222. Perhaps the greatest unifying factor was that while there was general consensus among Japanese leadership for what they termed the "Greater East Asia Co-Prosperity Sphere", the nature and extent of that Sphere was often in flux. The road to war for Japan was often slap-dashed and kludged together, rather than the product of a grand, overarching plan, so it's not surprising that planning for the post-war was late and similarly ill-fitting. The nature of the Co-Prosperity Sphere could range from a small formal empire, but with economic dominance over China and others; to a more expansive vision that included China, Indochina, the Indies, and sometimes even Indies as effectively colonial subjects, providing resources and captive markets to Japanese industry; or even a more economically co-operative version where Japan would assist the former European colonies of Asia with further economic development.
However, the core ideal of the Co-Prosperity Sphere--and Japan's overall post-war dream--was that of an East Asia where Japan stood ascendant over East Asia. The precise nature of how this vision would be implemented regularly changed, and there was little formal development into how the Co-Prosperity Sphere would be administered. The Japanese attitude towards to the Sphere also shifted over time, going from a more economically exploitative mood when Japan seemed ascendant over East Asia, to more co-operative, when Japan sought to utilise its 'allies' in its conquered territories to support the war effort and craft a propaganda image of an Asia united in opposition to the return of the Western Allies.
There's of course, much more that can be discussed here, particularly as it comes to the reactions of local peoples to the eviction of their previous colonial rulers and the arrival of the Japanese.