There are a number of other possibilities here. They include:
- Adherence to the laws of war. The Germans generally adhered (when dealing with prisoners from the Western Allies, at least) to the Geneva Conventions. They did not abuse prisoners of war on a systematic basis. This was very different from the Japanese who were extremely harsh with their prisoners. The Japanese had not signed the Geneva Conventions, but their abuses of their prisoners were abhorrent nonetheless.
- Willingness to surrender. The Japanese were much more determined to fight to the end than the Germans, both on an individual basis and as a country. The Germans did not do anything like the kamikaze attacks that the Japanese engaged in. Germany as a whole surrendered when it would still have been possible to fight while Japan did not surrender until two atomic weapons had been dropped on their soil.
- The Japanese government trusted its people more and involved them in the war effort to a greater degree. The Nazis worried about uprisings and so did not ask the German people as a whole to go through things like rationing. They did not get women to work in war industries. The Japanese were not worried about the obedience of their populace to anything like this degree.