Requiring a carrier-capable, long-range over-water performer for the reconnaissance role, the Imperial Japanese Navy (IJN) of World War 2 (1939-1945) invested in the development and subsequent procurement of a new type of combat aircraft - the C6N "Saiun" ("Painted/Iridescent Cloud") from the Nakajima Aircraft Company. The aircraft had origins in a 1942 requirement and flew for the first time, in prototype form, on May 15th, 1943. Series service began during August 1944 and this effort led to serial production run of 463 total units before the capitulation of the Empire of Japan (and the formal end of World War 2) during August of 1945.
The original requirement sought a performance-minded type capable of sustained 400 miles-per-hour that could range out to 2,875 miles. This resulted in the Nakajima "N-50" tandem-twin-engine proposal which eventually morphed into a more traditional design arrangement to benefit from the still-in-development Nakajima "Homare" radial of 2,000 horsepower. Despite its potential on paper, the engine was actually less than advertised, resulting in a key focus on airframe weight-savings elsewhere in the Nakajima design to compensate.
On the whole, the aircraft was given a highly conventional design form that included a nose-mounted engine placement, in line seating for the multi-person crew, and a single-finned tail unit. The mainplanes were low-mounted along the sides of the very slim fuselage and fitted slightly ahead of midships. The undercarriage was retractable and of the "tail dragger" arrangement for ground-running. One of the more distinguishing physical qualities of the aircraft was its long-running "greenhouse-style" canopy which covered all three crewmen - the cockpit section ran nearly half the full length of the entire aircraft.
The engine at the focus of the design was the in-house NK9B "Homare 11", an 18-cylinder air-cooled, radial piston powerplant driving a three- or four-bladed propeller unit at the nose. Outputting 1,991 horsepower, this powerplant attempted to provide the streamlined and lightweight frame with exceptional straightline speed - speed becoming the primary means of survival for the C6N as only a single 7.92mm Type 1 machine gun would be carried on a flexible mounting at the rear cockpit for self-defense.
Because of the underperforming Homare, Nakajima worked in another twenty-three prototypes to follow the original in an attempt to iron out standing issues and to hasten overall development. Despite this, the engine never lived up to expectations and this additional work ultimately delayed the aircraft's arrival into wartime service by some margin.
Initial operational versions were designated "C6N1" and initial results were quite impressive as the lightweight aircraft could often outpace pursuers sent to greet it - even the fastest American Navy types such as the Grumman F6F "Hellcat". Despite its development as a carrier-capable reconnaissance aircraft, losses for the Japanese by the end of 1944 and beginning of 1945 meant that C6Ns were generally operated from land bases for the remainder of the war.
The "C6N1-1" was proposed as a projected torpedo bomber, retaining its crew of three, but the need for such a flying weapon waned as Japanese losses mounted across Asia and the Pacific. The "C6N1-S" was a dedicated night-fighter (converted from the existing C6N1 stock) which reduced the operating crew to two, included applicable night-fighting equipment, and carried 1 x 30mm Type 5 or 2 x 20mm Type 99-1 automatic cannons in an obliquely-angled mounting (this weapon arrangement allowed the attacker to move under enemy bombers and unleash a lethal shot of cannon fire into the vulnerable belly through the upward-angled guns). However, Japan's radar network reduced the overall effectiveness of this much-needed bomber deterrent and the night-fighter form's value was extremely limited.
At least five other test projects related to the C6N emerged including the "Model 12" with its turbocharged Homare engine and four-bladed propeller unit, two prototypes being completed from the C6N1 stock. The "Saiun Kai 1" was a proposed, twin-cannon-armed high-altitude night-fighter that went nowhere. The "Saiun Kai 2" was to house the Mitsubishi Ha 43-11 Ru turbocharged engine of 2,200 horsepower but only a single prototype was partially completed before the end. The "Saiun Kai 3" was another proposed torpedo bomber form and the "Saiun Kai 4" was to rely heavily on wood in its construction due to resource shortages in the Japanese war effort.
The C6N was never exported and saw retirement as soon as the war ended in 1945. All examples in existence were either test units or operated under the IJN banner across general air groups and some three kamikaze squadrons.
As an interesting aside, and despite the inherent speed of the aircraft, the C6N series has the distinction of becoming the last aircraft to be destroyed in the whole of World War 2 - this unfortunate C6N1 example falling victim to Lieutenant Commander Reidy of the United States Navy on August 15th, 1945.