Except, Japan hasn't engaged in any form of imperialism in 70+ years. They are a completely pacifist country, not just in law but in actions. The same cannot be said about China who are now building military bases in Africa. They are also incredibly aggressive in the region.
> majority of Japanese people did support Japan's invasion in China during WW2. And this fact is never mentioned in any text books
You've fallen victim to propaganda I'm afraid. They most certainly do mention it in textbooks. Not just that, but they talk about Japan's atrocities like Nanking. Stanford University did a study which proved Japan's textbooks are more accurate than China's, South Koreas and Americas, less nationalistic too. See for yourself: http://www.nippon.com/en/in-depth/a00703/