People were seriously predicting that Japan was going to take over the world.
An interesting cultural document of this time is the 1991 (released just before the Lost Decade) movie Godzilla vs. King Ghidorah, where Godzilla is shown helping the Imperial Japanese Army and killing American soldiers during the Pacific War, and the plot of the movie is aliens going back in time to prevent Japan from becoming the global economic superpower that it is in the future.
In a similar vein, you can see cartoons either produced in the late 80s or derivative of works from that era portray Japan as (essentially) a superpower--pivotal figure in the capitalist bloc, target of left-wing terror factions, even Japanese veterans from wars in South America!
