Mitsubishi Ka-8

During early 1930s the Imperial Japanese Navy showed interest in the concept of two-seat fighters, as it was popular with foreign air arms. Therefore they ordered a prototype of the Nakajima NAF-1 6-Shi two-seat fighter in 1931. Albeit the NAF-1 was unsuccessful, IJN's interest in two-seat fighters persisted and in 1933 they requested designs for carrier-based two-seat fighters both from Nakajima and Mitsubishi.
Mitsubishi submitted a design, which they named the Ka-8 and the IJN named it Mitsubishi Experimental 8-Shi two-seat fighter. It was a single-engine biplane made out of mixed wood and metal. It had duraluminum spars in its single-bay equal-span staggered wings with wooden ribs and fabric covering. Fuselage structure was made out of welded steel tube with fabric covering with pilot and gunner/observer sitting in tandem in open cockpits. It was armed with two forward-firing 0.303in Vickers machine guns plus another defensive one mounted flexibly in the rear cockpit and it also could carry a small amount of bombs under the wings.
A twin-tail was fitted and it had a fixed undercarriage. It was powered by a single Nakajima Kotobuki which delivered 580hp (430Kw) of power and was a license-built version of the Bristol Jupiter radial engine.
Two prototypes were made by Mitsubishi the first of which was completed in 1931, with both of them being delivered to the IJN later in that same year. The second prototype broke-up when performing diving tests at Yokosuka on 16th September 1934. The pilot managed to escape by parachute but the observer in the rear seat was killed. That accident caused testing of the second prototype to be abandoned, with the other contender, the Nakajima NAF-2 being also rejected and the IJN abandoning the two-seat fighter category.

Sources:
1. https://en.wikipedia.org/wiki/Mitsubishi_Ka-8
2. https://forum.valka.cz/topic/view/48242
3. Salamander Books - The Complete book of fighters