The Nakajima NK1F Sakae 21 engine gave the plane slightly better performance, and the armament was changed to 2- 20mm and 2- 13.2mm guns. These changes did not make up for the lack of armor, or the lack of self-sealing fuel tanks. However,despite these shortcomings, over 10,450 were built, being used during the entire war because other models of Japanese aircraft continued to have “teething” problems.

