There are some definite oddities in the German-Japan alliance in the second world war:
-Both nations were racist nationalists who thought they were naturally superior. Both allied with a nation who very much was NOT their “superior” race
-Their alliance was almost never relevant. Did they ever meaningfully work together? (Arguably Japan got by FAR the better of the deal, as Hitler declared war on the USA, pulling an awful lot of focus, but Japan never invaded the Soviet East, which would arguably have pulled a ton of attention away from the German invasion in the West.)
But of course at the same time, both nations achieved, for a time, stunningly amazing military victories.
So what did the average German think when he heard about, say, the fall of Singapore? What did the average Japanese civilian think when he heard about the fall of France?
Did German or Japanese civilians ever visit each other as tourists? Would they have been welcomed? What was the general attitude towards the ally from the other side of the world?
The average German thought about Japan seldom, if at all. The two countries occasionally exchanged diplomatic visitors and attempted to share technology. However, the practical realities of distance and transportation - especially during wartime - made such coordination rare or impossible. They were essentially fighting two separate conflicts, linked only by mutual interest.
The one German who thought most about Japan was probably Hitler himself. Hitler was fascinated by Japanese culture and the pseudo-mythical idea of bushido. The myth of the fanatically loyal samurai retainer appealed to him for obvious reasons, and Hitler attempted to style the SS along the same lines. The SS motto, “My honor is loyalty” was an attempt to transplant the samurai ethos of loyalty above all else.
At the strategic level, Japan was useful because it provided a counterweight to Russia and the US. Hitler feared the inevitable Anglo-American alliance and Japan’s activity in the Pacific attacked US and British interests. Hitler also feared the Soviets. He initially considered the Chinese as potential allies against the Soviets, but when they signed a nonaggression pact with Russia that left the Japanese as the only remaining antagonist on Russia’s Eastern extreme.
Firstly, Japan had been defeated at the Battles of Khalkhin Gol in 1939. The Kwantung Army, which the Japanese regraded as their best unit, had been crushed by Soviet forces. The Japanese had no appetite to try again.
Secondly, the extremists who ran the Japanese government made the decision to turn south and seize territory and resources (especially oil and metals) in southeast Asia and the Pacific. Such a strategy would make it both difficult and extra risky to reopen the conflict with the USSR in the north.
But that didn’t make the Army reluctant to attack the Soviets in 1941. The Imperial Army planned to do exactly that in the months after the German invasion, though as far as is known not in direct coordination with Germany. They even got approval from the cabinet to put the early stages of the plan in motion, putting the forces in place and assembling supplies. It was a force far larger than the single reinforced infantry division defeated in the Nomohan War (as the Japanese called it) in 1939, over 20 divisions, and concentrated in eastern Manchuria to attack eastward through forests against the Soviet maritime province. Nomonhan was a border dispute along the western Manchurian/Mongolian border in treeless terrain.
The cabinet only finally rejected this plan in August 1941 in favor of ‘go south’ to break the US/British/Dutch oil embargo. That was more the navy’s idea, with the army relatively reluctantly following along. In Japan’s weird political system in the 1930’s and WWII there wasn’t really one set of extremists. There was a nominal power structure of emperor, cabinet, Diet which was not exactly in charge (especially not the Diet) v unofficial military influence from behind the scenes, but it wasn’t one unified military clique either, and the unofficial influences didn’t have any accountability.
There was some positive propaganda in both Germany and Japan about the successes of the other, humiliations of their joint enemies where that occurred. Also for example the Japanese submarine crews which visited France were featured in German media, stuff like that. But basically as has been said the man in the street in Germany and Japan gave much less thought to the war effort of their distance quasi-ally than average people in the US and Britain about one another’s war effort.
The Germans had a handful of U-boote deployed in the Indian Ocean & Pacific, used both to torpedo cargo ships and to bring Japanese stuff back to Europe (rubber in particular). As far as I know that’s the only “joint” military effort the two countries had. Scare quotes because they didn’t really coordinate with the Japanese at all and kind of did their own thing.
Germany also tried to transfer a tank to Japan via submarine, due to the Japanese lagging behind in that technology in WW2. IIRC, the ship went missing during the voyage to Japan and was never found.
or even, when talking about the turn south, into south-east asia, (especially rubber).
Japan had a shortage of oil during WWII because they were in WWII. They had a years supply of oil (!) going into WWII, and one of the triggers of WWII was that the Japanese were stockpiling oil so that they could go to war. If it wasn’t for the “going to war” bit oil wasn’t one of their resource problems. Rubber was a critical resource.