The Koku Hombu put out a requirement, in 1939, for a long range reconnaissance bomber that could operate from bases in Manchuria. It was to meet these specifications:
- Range: 3,107 miles / 5,000 km
- Cruising Speed: 280 mph / 450 km
To meet these specifications the designer, Dr. Kimura, proposed using a pressurized cabin. As this was still under development the Ki-74 project had to wait.
In late 1941 the aircraft was to be able to bomb the United States mainland. Self sealing fuel tanks and armor was added to the design.
The only defensive armament was in the tail and it was a remotely controlled 12.7 mm Ho-103 machine gun.
The Ki-74 was of all metal construction.
Initially the Allies thought the Ki-74 was a high speed fighter and gave it a code name of Pat. When it was found that the Ki-74 was really a bomber it was changed to Patsy.