Going back to OTL, and also in the book, Germany and Japan's alliance was always more of one of convenience and "spheres of influence." Germany and Japan really didn't aide one another in WWII. And in Nazi racial ideology, the Japanese were seen as inferior (which the book touches on). I always took Germany and Japan's Axis alliance as more of a "the enemy of my enemy is my friend" situation as opposed to genuine friendship.I definitely wanted you to have first crack at the names just want to be sure you were interested in all of them. I guess what Im wondering about is that based on events in the timeline it seems that at one point between WW2 and the present the Reich and Japan seem to have been .much closer with the Reich nuking Sydney for Japan in WW3 and allowing them to establish the base in San Diego (and take Alaska and Hawaii ?) Why was the Reich so generous with them unless they really were friends-as they were on the paper of the Axis pact OTL ?
Looking back, maybe the Reich wouldn't have nuked Sydney (maybe the Japanese did that on their own). Definitely flexible on that point.
The other example in media would, of course, be High Castle. I feel that in that series they really had Japan too far behind Germany technologically to make sense, but I think the tension between the Reich and Imperial Japan that the show portrays isn't unimaginable.
And Turtledove basically alludes to a present Cold War-like situation of MAD existing between the two empires to explain why they both allowed the other to exist (or probably more accurately, why the Germans ignored their own racial ideology when it came to Japan.
If anything, ITTL, the Japanese and the Germans have a cordial relationship all the way up through WWIII, and now with the United States gone and the two of them being the only real superpowers, tensions slowly rise and relations between the two empires cool.