When WWII began in 1939 Japan was an aeronautical giant; one of the top five aerospace powers on Earth. Six years later the industry lay in ruins and a year after that, no longer even existed on paper.
With the possible exception of Mitsubishi, very little was ever written about Japanese aerospace companies before WWII and most were unknown outside of their homeland; in contrast to companies like Messerschmitt or Boeing which were famous worldwide. Nearly no attention at all was given to what happened to them after WWII.
A study of their final fates also has a second story. This is how defense contractors – which dominated Japan’s GDP during the early 1940s – were dismantled in a controlled way to limit the “contagion” of their loss to the wider postwar economy.
(Mitsubishi’s bombed-out factory at Nagoya at the end of WWII.)
(The Nakajima Aircraft corporate offices in Ota during the post-WWII American occupation. Today a Subaru factory; one of Nakajima’s descendants, is on these grounds.)