Designed by T. Koyama, the Nakajima Ki-84 Hayate (Gale) was without question the best Japanese fighter built in large numbers during the war. It had a better rate of climb and could outmaneuver all of the advanced US fighters like the P-51H and P-47N, a fact discovered when one example was captured and tested. In contrast to other Japanese fighters, the Ki-84 did not sacrifice neither pilot protection nor armament to achieve its dogfighting ability but was hampered by poor quality controls as a result of hurried production and a high-maintenance engine; combat units would frequently suffer from accidents, shortages, and poor serviceability the result being that later versions even substituted aluminum for wooden parts. Unfortunately, B-29 raids against the engine plants during the final year of the war prevented larger manufacturing runs which could have made victory far more costly to the Allies had more Ki-84s been deployed in time. Despite these shortcomings, the Ki-84 gave a good account of themselves over China, Taiwan, the Philippines, the Ryukyus, and the Japanese homeland itself.

First flown as a prototype in April 1943, pre-production aircraft began equipping units in China in March 1944. The Production Ki-84-I was first flown against US forces in the Philippines to great success and was available in various different armament configurations which included the Ki-84-Ia, -Ib, and the -Ic which was a dedicated bomber-destroyer with two 20-mm cannon in the nose and two 30-mm cannon in the wings. Later, the Ki-84-II was built with a number of wooden fuselage parts due to the scarcity of aluminum during the final months of the war. Among other designs which never entered production were the all-wooden Ki-106, the Ki-113 which had extensive use of steel in the airframe, and the lightweight Ki-116 equipped with the Ha-32 engine.