As soon as the Imperial Navy had expressed its satisfaction with the performance of the Ka-14, the Imperial Army placed a contract with Mitsubishi for a modified example, fundamentally similar to the second prototype, for evaluation as the Ki-18. Powered by a Kotobuki 5, like the first Ka-14, the Ki-18 introduced a longer-chord engine cowling, an enlarged rudder and larger main wheels and spats. Tested throughout the autumn and winter of 1935, the Ki-18 carried the standard twin 7.7mm gun armament, but was considered insufficiently agile by conservative Army test pilots, and failed to gain favour. Nevertheless, the Ki-18 encouraged the Army to accept the coming demise of the biplane as a fighter configuration, resulting in the framing of a requirement for what was termed an "advanced fighter".