Evolving from the Kawanishi N1K1 "Kyofu" floatplane, the Imperial Japanese Navy's N1K1-J Shiden had a unique pedigree among WWII landplane fighters of the world. In January 1942, Kawanishi Aircraft began adapting the Kyofu into a land-based fighter, strictly as a private venture. This project was soon officially authorized under the designation N1K1-J, with the first prototype flying in December 1942. The airframe was basically the same as its predecessor, with main landing gear and tail wheel replacing the floats. In place of the Kyofu's Mitsubishi Kasei engine, a more compact and powerful Nakajima Homare engine was installed. Excellent performance and superb manoeuvrability was achieved using this engine; however it brought about serious problems. In order to use all of the available power in the engine, a large diameter propeller was required. This required unusually long main landing gear legs due to the midwing configuration, causing difficulties in the landing gear retraction system. Kawanishi engineers managed to solve the problem by introducing telescopic main landing gear legs. The complex gear system and unreliability of the engine plagued the N1K1-J throughout its career, until the introduction of the improved, low-wing N1K2-J Shiden-Kai. About 1,000 N1K1-J fighters were produced and were active around the Philippine islands, Formosa, Okinawa and over the Japanese island of Honshu.