The similarity between the Kawasaki Ki-61 single-seat fighter and the Messerschmitt Bf-109 led the Allies to erroneously believe that the Japanese aircraft was a licence-built version of Messerschmitt's famous fighter.

The Kawasaki Ki-61 was powered by their version of the Daimler-Benz DB 601A, known as the Ha-40, being completed in mid-1941.

More than 30 production examples of the Ki-61 were completed by the end of 1942.The type was a cantilever low-wing monoplane with a conventional tail unit, retractable tailwheel landing gear, single seat accommodation beneath a transparent canopy, and power was provided by the 1,175 hp ( 876-kW) Kawasaki Ha-40 engine. When the Ki-61 began to enter combat operations from New Guinea in April 1943 the type was quickly found to be an outstanding aircraft, well able to hold it out against Allied fighters. As production began to build up the Ki-61 appeared in all theaters where the Japanese army was operating, soon receiving the Allied codename "Tony"