Eventually after occuping all of "China" (real China, not including Tibet which was internationally recognized independent and Uighur northwest areas which was functionally independent) the Japanese almost certainly would run a foul of USSR regarding Uighur and Mongolia influence, probably more arrangements are found and no war.
Now Japan, by 1945 with no distractions of occupying Philippines, Indonesia, Burma, etc, can have effectively controlled China (warlord puppets for places like Hunan, Yunnan; not uncommon for Chinese dynasties, most used local autonomous warlords who had paper loyalty, Chinese will accept this). Japan will eventually have to face that European treaty ports are from treaties that they either accept or repudiate, France, UK with two, Portugal, and Italy all have cities. Depending on stresses in Europe and UK's distraction with Gandhi in India (without WWII there is a more militant revolution in India ATL). I see Japan increasing influence in Thailand, funding revolutions amd terrorist activities in IndoChina, Phillipines, British Malay, and Dutch East Indies, even fund Hawai'i activists demanding autonomy or indeoendence; show of force with navy making calls on ports, even a "world tour" a la US Commodore Perry's White Fleet (OTL Japan having their navy in the Mediterranean during WWI was a big source of pride for them).
Purchasing Wehei from Britain, Kwantung (sp?) from France, Italy's city, and ending extraterritoriality in Tietsin and foreign districts. Japan is seen as China is today and does similar activities such as technical support, money, and building expertise to "third world" nations- US worries about Japanese doing such things in Latin America, possible Japanese company talks about a canal in Nicaragua, influence in Peru, Chile, Brazil. Japan moves in to investing in Australia seriously becoming a major trading partner and owner of industrial production as British investment slips. Trucial States, Oman, Zanzibar, Kuwait, Ottoman Empire, and Ethiopia all see influx of Japanese investment and influence and of those that are British like Kuwait may start to reconsider their voluntary status in the British Empire.
As oil becomes more developed in the region thanks to Japanese technical support and Japanese ownership of the rigs the British can become seriously worried. France, Australia, NZ, British, Canada, and the US thanks to part racism, part economic and part geopolitical jealousy end up with possiblilities of how to deal with the rise of Japan. Without the horrors of WWII I would lean towards a continuation of haughty European and American exceptionalism that can lead to Cold War as Japan gains post-colonial third world allies to join it and Thailand in a Japanese led coalition of nations following "the Japanese way of capitalism". Proxy wars between Western backed nations and Japanese backed nations, coups and counter coups.