So, on top of getting nothing out of a campaign against the Soviets, the Japanese foolishly throw their entire army into Manchuria (etc.) leaving the home islands undefended along with other areas requiring garrisons. They denude their merchant fleet to move these troops to China and wreck their economy.
Maybe you should rethink your above scenario a bit before making absurd claims about what could be done.
By the by, the US Army Order of Battle of the Japanese Armed Forces 1 Sept 1945 lists only 125 divisions (including many that were previously destroyed) in existance during WW 2 for the Japanese. Just thought you might want to know that.
If anything, it seems the whole scenario is geared to providing a means to give the Germans a win in the East rather than the Japanese. I doubt the later nation would have been so cooperative in a losing venture for another nation they had no close ties to.