In order to make a final decision, two further prototype were ordered from both Mitsubishi and Nakajima, with Mitsubishi instructed to change its own 615 kilowatts Mitsubishi Ha-6 radial engines for the Nakajima Ha-5 engines used by the Nakajima design and vice versa, while the Ki-21 gained a revised glazed nose similar to that of the Ki-19 and revised tail surfaces.