The Nakajima Ki-63 was the designation given to a version of the Nakajima Ki-62 that would have been powered by the 1,050hp Mitsubishi Ha-102 radial engine. Both aircraft were designed in 1941 by a team led by T. Koyama, and were seen as back-up designs in case the Kawasaki Ki-61 was a failure. In the event the Ki-61 was judged to be a success, and so both Nakajima designs were abandoned. The work wasn't entirely wasted, as much of the knowledge gained was used on the excellent Nakajima Ki-84 Hayate. Kawasaki themselves would eventually be forced to use radial engines to power their own fighter, producing the Ki-100.