The only aircraft design of the Rikugun Kokugijutsu Kenkyujo (Army Aerotechnical Research Institute) that was actually flown during World War II was the Ki-93.
The Ki-93 was designed to attack bombers at high altitudes and ships at low altitudes.
The Ki-93 was designed to carry a large cannon under the fuselage for attacking Allied bombers or ships.
In the rear cockpit was a 12.7 mm Type 1 machine gun.
The two Mitsubishi Ha-214 (2,400 HP) engines drove six blade propellers.
The engine nacelles were armored. The Ki-93 had self sealing fuel tanks with automatic fire extinguishers.