Ki-61-I - first production version, launched in production in August 1942. Until July 1944 was built about 1380 machines two options - Ki-61-1A and Ki-61-1b. which differed from each other arms. On the Ki-61-1A it consisted of two 7.7 mm type 89 machine guns placed in the wings and two 12.7 mm type 1 machine guns above the engine. On the aircraft Ki-61-1b wing machine guns had the same caliber as those located in the fuselage - 12.7 mm. To increase the firepower of the fighters on 388 machines variants Ki-61-1A and Ki-61-1b instead of wing machine guns were installed purchased in Germany in August 1943 20-mm mg151 gun. This replacement required some strengthening of the wing structure in the area of placement of guns and installation of small under the wing fairings.
