The Imperial Japanese Navy ordered development of the Kyūshū Q1W as the Navy Experimental 17-Shi Patrol Plane in September 1942, and the first test flight took place in September 1943. It entered service in January 1945. The Q1W carried two low-power engines, allowing for long periods of low-speed flight, and was the first purpose-designed anti-submarine warfare aircraft in the world.
In same period Kyūshū built the K11W1 Shiragiku, a bomber training plane (also used in Kamikaze strikes) and the Q3W1 Nankai (South Sea), a specialized antisubmarine version of the K11W. The latter was of all-wood construction and was destroyed during a landing accident on its first flight.
Another specific anti-submarine airplane was the Mitsubishi Q2M1 "Taiyō" (which was derived from Mitsubishi Ki-67 Hiryū "Peggy" Torpedo-bomber), but this did not progress beyond the preliminary design stage.