The Kyushu Q3W1 Nankai was a dedicated anti-submarine warfare aircraft based on the K11W trainer. The K11W1 was a single engined crew trainer, with a two-seat cockpit and an internal cabin with space for three men. It was then developed into the all-wooden K11W2, which was used for anti-submarine warfare. This was followed by the dedicated Q3W1 Nankai (South Sea). This retained the basic layout of the K11W2, with a circular fuselage and large wing with a straight trailing edge and tapered leading edge. It carried a crew of two with the remaining space allocated for anti-submarine warfare equipment. A single prototype was produced, and made its maiden flight in January 1945. This first flight ended with a wheels-up landing, and after that work on the project was suspended and didn't resume before the end of the war.