The Ki-9 was a two seat unequal wing biplane design. Tachikawa originally planned to use the same basic airframe for both basic training and intermediate training, differentiating the two models by the use of different engines. The prototype Ki-9 flew on 7 January 1935, powered by a nine cylinder Hitachi Ha-13a radial engine. The second prototype was identical, and the third prototype was powered by a Nakajima NZ seven-cylinder radial engine. The third prototype exhibited stability problems due a center of gravity issue, and as a result the primary trainer model was abandoned and the Ki-9 was developed only for the intermediate trainer. Tachikawa subsequently developed the Ki-17 for the primary trainer role. The first production aircraft were delivered in 1935.