This isn't terribly hard. Have the Germans pursue an alliance with the KMT rather than the Japanese, and then you have a slightly different Axis (Germany, Italy, and China), and a Japan that's still effectively fascist, but allied with the Allied Powers. The war is going to be quite different, and you'll have to figure out how to get the United States into the war without Japan attacking Pearl Harbor, but it's doable (unrestricted naval warfare ala World War I might do the trick)
China, of course, is going to be a bitch to defeat, but with Soviet and British help, it may be possible for the Japanese to actually subdue it. The war probably finishes up a bit earlier than IOTL, and Japan becomes a founding member of the United Nations along with Britain, France, the USSR, and the US. The Japanese keep a lot of their empire, but it eventually crumbles under the pressure of anticolonial movements in the fifties and sixties, as well as left-wing students' and labor movements at home demanding democracy.
By the modern day, Japan has shed most of it's empire, though it still retains southern Sakhalin, the Korean peninsula, and Taiwan. The Democratic Republic of Manchuria is a constant headache on the Asian continent, and the Chinese Republic is a rising economic power. Tensions with Japan are lower than what they were in years passed, though there is still a lot of tension concerning Taiwan, which the RoC claims is it's and Japan claims is it's. Japan itself has a somewhat less democratic constitution than OTL, but is widely considered a liberal democracy, and is currently ruled by the Japan Socialist Party.