In 1942 the Koku Hombu brought specifications for a new fighter to Nakajima. In November 1942 an order for three prototypes to be completed by January 1945 and for seven pre-production by April 1945 was made.
- Speed: 497 mph / 800 kph
- Range: 1,864 miles / 3,000 km, later lowered to 310 - 497 miles / 500 - 800 km
- Armament: two 20 mm and two 30 mm
A Nakajima Ha-44 11 or 21 (2,400 HP) was selected. A turbo supercharger was mounted on the starboard side of the nose.
Two 20 mm Ho-5 cannons were placed in the wing roots and two 30 mm Ho-105 cannons outboard of the landing gear.
The landing gear was made to turn 90 degrees so it would lay flat in the wings.