The German in-line DB.601 engines showed great performance which forced Japanese military to build a fighter powered with this unusual (for Japanese "radial" powered aircraft industry) engines. Of the two companies that presented similar proects, the Kawasaki Ki.61 was chosen because this company produced the licensed DB 601 engines. The Nakajima project never reached a prototype stage, and actually was a transition design between the Kt.43 Hayabusa and the Ki.84 Hayate. The latest was in fact an overdimensioned Ki.62