Contrasting with the Nazis who worked out exactly how many people of each conquered country was to be killed or enslaved, the Japanese didn't have much of a master plan for how they would handle the massive population of its Asian territories. From what I've read, the stated goal was to create good conditions across Asia for Japanese to settle outside their overpopulated islands, do trade, and "civilize" countries of Korea, China, etc.
In mass murder the the Imperial Japanese Army seemed to take a pragmatic (if you can call it that) view; for example, they saw the use of massacres and biological and chemical weapons to kill Chinese soldiers and civilians as a good military strategy to help them defeat the "bandit" Nationalist Chinese government, and bring order to Asia. The rationale was that there were just too many Chinese and the IJA needed every technological advantage it could get to win.
In Manchuria, which was seen as the Japanese version of lebensraum, they were content to import millions of laborers from Chinese proper to build up the industry and infrastructure there, albeit under such poor conditions that this human capital was being routinely buried in "10,000-man graves" after they died from overwork. At the same time, Japan wasn't out to dismantle Chinese cities brick by brick or turn Beijing into a lake, Generalplan Ost-style. They wanted a subservient China dominated by Tokyo, and this country would probably serve as the center of their pan-Asian empire.
Pan-Asianism as an ideology wasn't ever properly codified, but based on what the Japanese academics did talk about and the actions of Japanese officials, it's pretty certain it entailed developing industry and society across the empire, but with the condition that Japanese people, laws, and culture were superior to everyone and everything else. From the experiences of Korean and Chinese collaborators, we can see that a good number of them liked their service enough that they learned Japanese and followed their bosses' orders pretty well. Likewise, ordinary people living under Japanese rule were often allowed to get on with their lives if they were in a relatively peaceful or well-developed area.
One observation I remember reading was that when the Japanese in some eastern Chinese city surrendered in 1945, the locals complained that the "dogs" (Japanese police who were harsh yet kept order) were gone, but they were replaced by "pigs" (corrupt Chinese officials who ignored the law). Another account I read from a Chinese person whose grandmother grew up in Manchuria during the occupation was pretty favorable to the Japanese since they did build the region up massively. Apparently some of those benefits did trickle down to some Chinese, but that wouldn't change the fact that they (and Koreans, Vietnamese, Indonesians, etc.) were second-class citizens in their own countries and that millions of their less-fortunate compatriots were being brutalized and slaughtered.
My guess is that if the Japanese "won" in Asia (defeated China, didn't get the Americans to intervene, or more implausibly, defeated the Americans), they'd continue their "pan-Asian" efforts to build a developed empire with Japanese being the local master race, and kill somewhere upwards of 50 million people in the process before running out of money and political energy.