There are several reasons that a Japanese attack on the Soviet Union, even at the height of the German invasion, would have failed.
First, the Soviets raised a new division for each one sent West from Siberia or Mongolia. The Soviets typically for most of the war maintained about 50 divisions in the Far East facing Japan. They also maintained parity or superiority in artillery and armor to Japan.
Second, the Japanese would have been literally hundreds of miles from the nearest rail head for supply. This means with every mile they advance their supply situation becomes more tenious. At Kalakin Gol the Japanese were 350 miles from their railhead and able to maintain just one infantry division at that position. The Soviets threw the equivalent of a reinforced corps against them and wiped out that divison,albeit at the cost of heavy casualities. But, then again, when have the Soviets ever been overly concerned with casualities?
Third, the Japanese army was in no way fit or capable of sustained large scale continential warfare against a major industrial power.
And, lastly, the Japanese get very little by invading. They don't aquire any major industrial sites, no major resources they really need and, no useful population for labor. If their invasion is for economic gain they get none from this course of action.

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Truth is stranger than bullshit!