The Imperial Japanese Navy acquired their first large flying boat from the British Short Brothers. The K.F.1 prototype flew on 10 October 1930 and was sent to Japan to become the model for the Kawanishi H3K2. As soon as these entered service a yet larger flying boat was demanded which led to the H8K2, known to the Americans as Emily. This was a long-range bomber and reconnaissance aircraft with four 1,850-hp Mitsubishi MK4Q Kasei 22 14-cylinder radial piston engines which gave it a performance of 289 mph at 13,125 feet and, at cruising speed of 183 mph, a range of 4,443 miles. An Emily carried five 20mm cannon and four .303-in machine guns. They could carry up to 2000kg of bombs or two torpedoes. The first mission on active service was undertaken by two Emilys in March 1942, the second attack on Pearl Harbor known to the Japanese as Operation K.
You can find out more about the flying boat Emily in the following Osprey books: