[2] The aircraft was designed in response to a Navy requirement of 1934 for a long-range flying boat and incorporated knowledge gleaned by a Kawanishi team that visited the Short Brothers factory in the UK, at that time one of the world's leading producers of flying boats, and from building the Kawanishi H3K, a license-built, enlarged version of the Short Rangoon.

[3] The "Type S", as Kawanishi called it, was a large, four-engined monoplane with twin tails, and a hull suspended beneath the parasol wing by a network of struts.

Three prototypes were constructed, each one making gradual refinements to the machine's handling both in the water and in the air, and finally fitting more powerful engines.

[6] Additionally production:[5] Sixteen (16) aircraft were civilian air transports operated by Dai-Nippon Airways (the Imperial Japanese National airline), with on board toilet, galley, and room for 18 passengers.

[7] Combat H6K were armed with various combinations of Type 92 machine guns, and it could also carry two torpedoes or 1000kg of bombs.

[9] On 15 February 1942, a P-40 Warhawk intercepted an H6K, about 190 km west of Darwin, Australia, which had attacked Allied shipping; both the P-40 and H6K were shot down.