Germany's
other Ally, Italy, were not Germanic, either.
However, Japan was essential to (a) destroy the British empire in the east, and there was a lot of it, don't forget, and most importantly, Japan had probably the best and largest modern Deep Sea navy in the world. Something Germany almost completely lacked. Cutting Britain off from its empire was very important, and also, America's entry into the war was no surprise to the Germans. They'd been expecting it for while.
Japan, though, was more interested in a "Mexican standoff" with the USA: give them a bloody nose (at Pearl Harbor), then retreat to behind a vast and distant "perimeter fence". The Japanese High Command did not believe that America would have the stomach for warfare over such a vast area and so far from their own mainland. Plus, since Hitler had been trying to get Japan into the war almost since the offset, any declaration of war against Japan was likely to provoke a German declaration of war against America. This, of course, happened. The Japanese believed that America
definitely would hesitate to wage war against both Japan and Germany. They probably also doubted that the US would ever ally itself with the USSR.
Whilst there was no way Germans could be seen as Japanese, or vice versa, both countries had similarities: both had godlike (in the eyes of their subjects) leaders; both required a martial spirit (and had a warlike, martial past); both believed themselves to be deprived in their past by "inferior" races and both believed that they were superior to their surrounding countries.
But it was Japan's navy and (hopeful) attack on the USSR which Hitler most hoped for. The only problem was, Hitler's hopes were not the same as those of the Japanese High Command, and even Yamamoto had doubts about war:
Should hostilities once break out between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians (who speak so lightly of a Japanese-American war) have confidence as to the final outcome and are prepared to make the necessary sacrifices