The Mitsubishi Ki-1 was a low-wing, cantilever monoplane with fixed landing gear, twin fins and rudders, and was powered by two Mitsubishi Ha2-II water-cooled V-12 engines, giving a maximum speed of .
The K37 prototype was brought to Japan and tested in combat during the Manchurian Incident of 1931, following which the Imperial Japanese Army Air Force authorized Mitsubishi to produce both heavy and light bomber variations.