Connection between Germany and Italy (and, while we're at it, the other European Axis Powers like Bulgaria, Hungary, and Romania) was pretty good, but German-Japanese connection was extremely poor. There are no easily-accessible routes between Germany and Japan, especially when they really become important (i.e. America's entry and the beginning of the Pacific War). Aircraft lacked the range, and there was next to no friendly territory for the Axis to land and refuel their planes anywhere between Europe and Japan. Ships would take a ridiculous amount of time, especially given that none of the major trans-ocean canals (Panama and Suez, namely) were friendly to the Axis, with those canals being the only way a ship could dream of getting between Germany and Japan in any reasonable space of time. There are no notable, if any at all, instances of Japanese forces fighting in Europe or of German forces fighting in the Pacific. Even if there were, the most either side could hope for would probably be a few dozen men at best, making it pretty much useless token support.