When two imperialist countries fight a war against one another its an imperialist war. Both sides will usually present themselves as the hero. That is true of ww2 as well. One bloc is a represented liberal democratic imperialism while the other represented fascist imperialism. On one side worker's lose, and on the other workers lose and are exterminated en mass.

After the war the US wrested control of the Japanese state, rewrote its constitution, and rebuilt the economy in a fashion friendly to US finance capital. They present themselves as altruistic rebuilds but that is a deliberate deception. Since WW2 the post war Japanese government has served as a junior partner to us imperialism in East Asia. The Japanese government supported the US during the Korean and Vietnam.