A key thing to remember when starting a game as the Rising Sun: rename your naval units immediately so you can look at the list and tell immediately what units you need to activate. Otherwise, they will all be the same name.
EDIT: For reference, my current Empire (by which I mean my direct control) is Japan, Korea, Taiwan, the Legation Cities, Shandong Peninsula, Hainan, former German IndoChina and the area to the north of Beijing. My puppet states are National China (basically all of China-Proper) and Fengtien (Manchuria), [forgot Transamur]. I have Thailand in my alliance.