This is the UF-XS flying boat (the photo by Itachi) with four piston engines being displayed at the Gifu Kakamigahara Air and Space Museum, Gifu Prefecture.
The purpose of developing the UF-XS was to incorporate technologies in such a way to allow takeoff and landing on the high seas. How was this done? In particular, the nose section is configured to suppress waves; two gas turbine engines are specifically installed over the central fuselage (can be seen over the cockpit in the above photo) to blow compressed air over flaps to drastically increase lift for STOL (short take short take-off and landing) capability.
The UF-XS was designed and manufactured by ShinMeiwa Industries, which happened to manufacture the navy’s flying boats in quantity during WW2. It made its first flight on December 20, 1962. For nearly 4 years, the UF-XS flew various test missions and collected valuable data. This data was aptly utilized for the subsequent flying boats that went into service with the Japan Maritime Self-Defense Force. The latest is the US-2 rescue flying boat.
This is Asuka with four jet engines uniquely mounted on top of the wings being displayed at the same museum. There is a definite logic for this engine mounting in that the jet exhaust gas blows over the top of wings to create more lift. Asuka made its first flight on October 28, 1985. For more than three years, Asuka managed to both complete numerous test flights and obtain valuable STOL data. Asuka was designed and manufactured by Kawasaki Heavy Industries as the main contractor in close cooperation with other Japanese aircraft manufacturers.
Besides Asuka, NASA, the US Air force and Russia also experimented with the same type of engine-mounting. Only Russia managed to put such aircraft into service, the An-72 military transport. The main reason for this limited application has been the high cost of development as well as the difficult flying characteristics typical for this type of engine mounting.