In our time line the failed assasination of Inukai Tsuyoshi spawned worry, concern but also the will needed to reign in the growing militarism of japans armed forces, the conflict between the growing facist movement in the armed forces and the conservative government came to a head with the invasion of poland. Concerned that the overly agressive troops in the armed forces would jepordize japans position in machuria Japan declared war on germany and used the war as a way to purge the most radical and at times disloyal elements of the armed forces, while securing its historic alliance with the british empire.
But what if Inukai had died? What would happen if japan Joined the axis powers?
I'm afraid the most obvious divergence from OTL might be that Japan gets A-Bombed along with Germany, or even instead of Germany if the Nazis get defeated early enough(IOTL, it took until June 1946 for the Nazis to surrender and it took our first atomic bombs destroying both Hamburg and Frankfurt to finally get Himmler and company to surrender). And then they could possibly find themselves divided just as Germany was.
P.M. Tsuyoshi's actions immediately after the attempt on his life, no doubt saved Japan from falling on the wrong side of history(while also not ending up as a total U.S. puppet as Korea did in response to the recently independent Manchuria going Communist in 1962; under the Wallace Plan, Japan was able to build a successful multi-party liberal democracy after the war, while Korea was dominated by a certain pair of right-wing strongmen from 1949 up until the January 1987 Seoul uprising).
OOC: Should clarify that, as per this post, Manchukuo became independent again in 1956, following the Japanese withdrawal of most active military forces a decade earlier, as part of a friendship treaty signed between them and the US; unfortunately, their one elected leader prior to the Revolutionary takeover, turned out to be much like Cuba's Fulgencio Batista, himself assassinated in 1956 ITTL.
The world would have gone a much darker path...
My guess is on an Allied victory but:
-The Soviet forces occupies Germany and annexes it, as well as Poland and Czechoslovakia, as part of a Soviet Socialist Republic
-China is the biggest mystery: An East (Pro-US) and West (Communist) China is very likely but the odds of having an entie Communist China would have been very high (either by a defeat of the Republican forces during the civil war or by post-war coup, like the 1952 Coup Attempt by Mao)
-Japan have two possible endings:
1) If the US manages to get the Atomic Bomb faster then in OTL, they could have used it on Japan as a way to make them stop all fightings. The possible targets would have been Tokyo, Kyoto, Hiroshima, Kokura or Nagasaki... Post-war Japan would need US assistance to rebuild itself and would have lost much of its influence on the Pacific and with former territories (Manchuria, Korea and China).
2) If Allied forces decided to invade Japan (which I thik is more likely than dropping nukes), Japan would have been split in two with a Soviet-occupied north and a US-occupied south. North and South Japan would be involved in a bloody civil war in the 1950s. A reunification is possible after the fall of the USSR (in 1993, like in OTL) but if not, then North Japan would be a pariah state with a possible nuclear arsenal that could be used, if necessary, on South Japan, China, Manchuria and Korea.
TBH, although I do think Mao's coup attempt, should it still happen, would have definitely have had more of a chance with a much weaker Japan, but the main reason it failed IOTL is because we indirectly intervened on behalf of the Japanese and the Pengist government in China, which was still shaky at the time. Although, one must wonder what kind of effect "Comrade Mao" might have had he not died in 1953(in March, 6 months after the coup, and, as it turned out, was taken out by the CIA) and been able to live long enough to escape to Manchuria when the pro-US and Japanese-friendly government there fell in September 1962: he was once almost universally popular amongst the Chinese left and is still admired today, much like former Bolivian president Che Guevara is in Latin America.