Now I'm not BSing, the Japanese army actually attempted hearts and minds in parts of China they had (or could conquer without facing international troubles) years before actual war broke out with China. Even early in the war before the major battles at Nanking and Beijing, etc the Japanese army wasn't doing mass pillage and rape when they conquered weak villages.
At least in the parts Japan had in Manchuria before the war, I recalled some genuine Chinese supporters from some book I can't remember to the point young men were volunteering for the Japanese army and Chinese civilians including women cheering for the Japanese during the middle of the war (and before war a significant amount of Japan's army in china was actually Chinese soldiers). Damn wish I could remember the name of the book so I could quote it.
Even fictional stories such as the manga Fist of the Blue Sky shows a complex relationship of the Japanese army in China before the major battles heading towards Nanking. For the example I use Blue Sky, pre war Japanese soldiers are obeying conventional laws (at least enough for news media to view the Japanese army as behaved though stuff like biological experiments pre war were touched upon). When a female Chinese guerrilla leader was captured, she was treated with civility on the Japanese side and she even was able to negotiate with a Japanese general to release her band (and he complied because he was so impressed by her). The Japanese imperials were shown as at least trying to use logic and common sense in trying to suppress the Chinese rebels (enough that they realized they were real human beings).
With all that said, this makes me wonder. Suppose Japan continued with hearts and minds as they blitzed through Asia after Pearl Harbor or at least had the common sense not to piss off their newly conquered nations, how does this affect the war effort?