Even attempting to deny Germany's war crimes is a criminal offense in Germany. As horrible as the Nazis' behavior was during the war, Germany has arguably done more than any other nation ever has to atone for its crimes after being responsible for an enormous number of deaths. I would argue that they've done more for the Nazis' victims than the United States has done for American Indians who suffered at our government's hands.
Japan, on the other hand, has never offered more than a half-hearted apology for any of its war crimes, and even those have come off as hollow. They're whole attitude is sort of like, "well, we lost the war, we got nuked, and we lost our Empire, so we got punished and we don't have to be sorry." Any compensation to victims of Japanese atrocities during that era has basically had to be coerced out of its government.
Angela Merkel doesn't get her feet held to the fire because the world knows that Germany is really sorry for what it did, and it's voluntarily compensated its victims both individually, and by offering support to the State of Israel, a homeland for Jews so that they don't have to be a persecuted minority in countries like Nazi Germany where they weren't wanted. It's countries that won't own up to their crimes, like Japan, that get held accountable.
Japan is a great nation with a history going back 2,700 years. For 70 years, it has been a responsible member of the community of nations, a world economic superpower, and in no way a menace to its neighbors. It wouldn't hurt them to swallow their pride and genuinely ask forgiveness for the actions of its government during the pre-1945 Showa era.