That's because China is always the prime concern by Japs...
If casualties count is the only way to quantify contribution, no other countires can beat China...
BTW, if it's not Southeast Asia, Japan won't attack US at Pearl Harbour. Do you think it's just madness for the Japs to declare war at the States?
I'm not arguing China doesn't have contributions during WWII. I'm more focus on the fact that if US didn't step in, it would be a totally different world. At least, China will have more places belonged to the Japs as colonies, just like the northeast in the 30's.
I'm more on Rainbow side, you are stating the fact based on the view as a Chinese, but not at the view of the local resident of those countries in the surrounding.
Every time when China, considered itself as a terrerstrial nation throughout history, tends to expand, it is always stopped by mountains and waters. And, you have to consider the factor of population growth too. It's the matter of fact if it's capable to sustain it or not... Territory expansion is always the dream for emperors years after years.
Again, I can only tell you can only read, but not to understand...