What would have happened is pretty clear since we know why both went to war, what they did during the war, and what they planned afterwards. The Nazi regime wanted a northern and eastern European Empire dominated by Germany. In said land, they planned to "depopulate" the area (i.e.
Murder/let the people starve/force off the land etc) to allow for German colonists. They would have finished off their "final solution to the Jewish" problem along with their solutions to the Slavs, Poles, communists, disabled, homosexuals, and Romani who were under their control. Then they would have murdered their disabled war veterans.
As the Japanese showed a great distain for the Chinese, I think we could have expected the continued genocide to take place there. I think we could also expect them to carry on their mission of driving out the European colonial powers from Asia, and replacing them with Japanese rule. Now considering the Soviet Union would still exist (or at least Soviet Russia and at any rate confined beyond the Ural mountains) along with India (as either an independent state, a Japanese puppet/ally, or still a part of the British Empire) an Italian Empire dominating south-east Europe along with the Mediterranean, North Africa, and probably the Middle East; there would have been buffer states between Imperial Japan and Nazi Germany.
The answer is, nothing would have happened between the two. There would have been no direct contact. Each lacked the means to send invasion fleets around the world, and even with the greater access to resources and industrial potential it seems unlikely either would have fought a war raging across central Asia.
We would all be saying "Hail Hitler" right now. The Germans would have made conquest of the entire world, including the Japanese.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.