Manchurian missiles is an acceptable stretch in a timeline involving the entire Japanese empire - it wouldn't mean victory, but it would make things more interesting. You couldn't hit a moving ship with a V-series I imagine, and they won't be good enough to reach L.A. or anything, but you could maybe lash out at big cities in the Pacific held by the Allies.
Or, forget the missiles and make the other part of the TL manchurian - Manchuko ends up surviving, as the highest ranking Chinese in the government take over, use Pu Yi as a figurehead as well, and employ Japanese scientists and industrialists in attempts to keep independent and from having their heads handed to them for collaboration by Chiang or Mao.
The Japanese intelligentsia would die off/be assimilated in a generation, but the history of brutality would last much longer.
Let us Say that the Japanese Army's in China retreated back to Manchurian
in 1944 and they started to build even Hetzer Tank Destroyers and up graded there arty with German designs and rotated Army pilots home after 6 mo they might of been able to held the Soviets off , Remember most of the Japanese Army was in China even at the end of the War.