This Soviet-Nipponese pact would be avoided as Germany delares war on Japan (by a secret German-Nippones agreement) but in name only and has no desire to have any conflict with Japan (infact no German and Japanese forces ever meet, actually the German declaration of war on Japan could work for both Japan and Germany as it forces the western allies to choose, it is like either sleeping with your sister or your mother both disagreeable but which one less tolerable.

I'll add more later.