Regardless of their actual in-universe history and actions, in any TL where Imperial Japan appears:
-The audience will expect them to act by robotically copying the actions, attitudes, and ideas of OTL's Imperial Japan even if that doesn't make any sense. (Like, expect Japan to try to conquer Korea even if the TL's point of divergence is Korea becoming Japan's ally vis-à-vis the outside. Or expect Japan to try to conquer China even if the POD is the ISOT of the People's Republic of China from 2022 to 1922. Or expect them to go genocidal insane in China even if the political focus is "Asia United Against The Colonizer"). And they will protest accusing the author of "whitewashing Imperial Japan" if they don't.
-They will repeatedly express their disbelief that ANYONE (except Nazi Germany) would consider not just allying with Japan, but maintaining diplomatic and trade relations with Japan. As well as his conviction that the focus should be on supporting and uplifting all neighbors (especially China) to "counterbalance Japan", and decreeing savage embargos with the only goal of destroying Japan's economy (and who cares about the commercial losses this policy surely will cause to their country). That's right, it seems Japan should be treated even worse than North Korea.
-They will make increasingly aggressive calls for the protagonist country to focus all its efforts on containing and destroying Japan, because "they are too evil to be allowed to live" even if it is a France that is understandably more worried about its neighbor : the openly genocidal, imperialist, expansionist Germany that is howling about how they want to conquer France and exterminate all French people.
-If the United States exists, the focus will shift to trying to convince the United States to throw its full weight into destroying Japan, ignoring China and the other Asian neighbors, because "we need the Americans in Asia" (even if it is a country that the presence of the United States in Asia would harm immensely in every way).