The Kawasaki Ki-100 was a single-seat, single-engine fighter aircraft developed by the Imperial Japanese Army Air Service during the final months of World War II.
It emerged as an emergency solution to a production crisis: in early 1945, Allied bombing raids destroyed the factory producing the Kawasaki Ha-140 inline engines intended for the Ki-61-II-KAI Hien.
With over 270 completed airframes rendered unusable, Kawasaki engineers retrofitted them with the air-cooled Mitsubishi Ha-112-II radial engine, resulting in the Ki-100-I Ko variant.
Despite its improvised origin, the Ki-100 proved to be one of Japan’s most capable fighters.
The radial engine was lighter and more reliable than the Ha-140, improving manoeuvrability and climb rate.
The aircraft retained the low-wing monoplane layout and enclosed cockpit of the Ki-61 but required a redesigned engine mount and cowling to accommodate the new powerplant.
The conversion was completed rapidly, and the first Ki-100s entered service in March 1945.
A second variant, the Ki-100-I Otsu, was a purpose-built model with a cut-down rear fuselage and a bubble canopy for improved visibility.
These were produced from May to July 1945, with approximately 118 units completed.
A final high-altitude prototype, the Ki-100-II, featured a turbo-supercharged engine, but only three examples were built before the war ended.
Operationally, the Ki-100 was deployed in home defence roles, intercepting low-flying B-29 bombers and escorting kamikaze formations.
Units equipped with the Ki-100 included the 5th, 59th, 200th, and 244th Sentai, as well as the 81st Independent Fighter Squadron.
Pilots praised the aircraft’s agility and reliability, and it was considered one of the few Japanese fighters capable of matching Allied aircraft such as the P-51 Mustang and F6F Hellcat in combat.
In total, approximately 396 Ki-100s were produced, including both Ko and Otsu variants.
Although it arrived too late to influence the outcome of the war, the Ki-100 remains a testament to Japan’s engineering adaptability under pressure.
