About my background first: I am german, in school history class we went through human history in order (starting in the antique going forward), eventuall we ended with the lead up to the Nazis coming to power in 1933: the great depression, not functioning political processes, etc - after that you basically spend a lot of time on Nazi Germany: goverment structure, daily live, the arming, maniqulation of the people using group dynamics, the regimes use of the media but also a heavy focus on resistance (and how it was shut down and silenced), "Mitläufertum"(=following blind, following because its easier then resisting) in the society and of course the Holocaust and the justification behind it as well as events like the Reichskristallnacht.
...all in all I have the feeling that you can assume that as a german you learn about how the Nazis came to power, what crimes "they" commited and how the people either joined, went along with it, shut their eyes or fought against it...how people were influenced by the media and sold ideas like the dagger legend or things like the economic situation being the Jews fault.
tl;dr: in germany you learn a lot about Nazi rule & crimes in school and beyond and while not everything is ideal, I think there is a healthy mentality of being aware of this dark chapter of history - as a way to see the signs and, well, honour the victims but also to reflect on our selfunderstanding as germans (that being the ideal case). I would say there has been some sort of mental cut (I know the cut wasnt always as clear as it is todaye) between nowday Germany and Nazi Germany.
To Japan: I have the feeling (everytime Japan and WW2 come up) that Japan never did this mental cut? That other than germany japan more or less carried on and things like crimes against for example the chinese people were never really reflected?
Post-WWII history of Japan is not my prime forte, but I do know that the current Japanese prime minister Shinzo Abe supports Nanking Massacre denial. You may find this piece (written by the Japanese historian and professor emeritus Tokushi Kasahara) interesting. It discusses how Abe's administration has been systematically reinventing the history of the atrocities committed by Japan in WWII.
EDIT: You may also want to look up the Nanking Massacre (a.k.a Rape of Nanking) if you're not already familiar with it. In quick summary, it was the mass rape and massacre that followed the capture of Nanking (then the capital of China) by the Japanese Imperial Army in 1937. More than 100,000 Chinese were killed in 2 months of raping, killing and pillaging.