The Japanese navy needed a plane that could cover the Japanese possessions throughout the Pacific Ocean. Yoshio Hashiguchi and Shizuo Kikahura, designers for Kawanishi, started to design the H6K in 1933.
The design took elements from the British Short Bros work in the early 1930s and American designs for the parasol wing. The H6K was based on the French Potez C.A.M.S. 141.
Was originally called the Kawanishi Navy Experimental 9-Shi Large-size Flying Boat.
The Kawanishi H6K "Mavis" could stay in the air for 24 (26) hours.
The H6K did not have self sealing fuel tanks or armor this causing them to be vulnerable to fighters.
The H6K was of all metal construction.
Originally there was a hand held 7.7 mm Type 92 MG, but in the H6K5 it was removed. It was replaced by a turret right behind the flight deck.
The parasol wing was mounted above the fuselage. The wing struts could carry bombs or torpedos.
After the initial test flights the forward step in the hull was moved back 20" / 50 cm.
The Japanese studied the Sikorsky S-42 and designed the H6K with a two step hull.
The tail gunner had excellent visibility through the glazed turret.