Even in this scenario the Japanese are going to be able to control the waters between Japan and Manchukuo, Korea, and at least North China for some time. The problem is that the resources of SEA are needed not just to fuel (literally) the IJA & IJN but all sorts of raw materials are needed to keep Japanese industry up & producing. You can only work around raw material shortages somewhat, and cheesing on metallurgy (for example) means armor less effective, engines less powerful (HP/kg) - this leads to increased fuel consumption..oops, and so forth. Other stuff simply can't be done without.
Even if ASBs let the Japanese create a military situation in China which was a "fait accompli", ITTL Japanese industry simply will not be able to produce the stuff they need to accomplish the task. Of course, a defense where we are now in the Pacific + go for broke policy in China will simply let the Allies send resources to China that OTL were used elsewhere. B-17's and B-24's have the range to attack industrial plant in Manchukuo, even before B-29's come on board to bomb Japan directly, and ITTL supplying these bomb groups will not require all those hump flights.