@Mulboyne:
National Museum of Nature and Science has discovered footage of the KEN III the Kawasaki Ki-78 research aircraft project, which was renamed the Kawasaki Ki-78 when taken over by the military during WWII. Apparently, only two prototypes were ever built.
Besides the Kawasaki Ki-78, Japan also had working versions of the following according to WW2 Aircraft Ranked-by-Speed website::
![Idea :idea:](./images/smilies/icon_idea.gif)
![Idea :idea:](./images/smilies/icon_idea.gif)
![Idea :idea:](./images/smilies/icon_idea.gif)