Designed by Takeo Doi, the Kawasaki Ki-45 Toryu (Dragon Killer) was the Japanese Army's first attempt at a long-range heavy fighter similar in concept to the German Bf 110. Like the Bf 110, it soon became evident that these aircraft were no match for single-engine fighters and thus the Ki-45 switched roles to become a successful ground attack and maritime strike aircraft as well as a bomber destroyer, employed against B-25s in the South Pacific and then against B-29s over the homeland. Later in the war, a night fighter version of the Toryu was introduced and even though it lacked radar, was the most effective of its type to be used by the Japanese thanks to very powerful armament and an oblique dorsal cannon; one squadron managed to shoot down eight B-29s in a single mission. Like most IJAAF aircraft, it was eventually employed as a kamikaze starting with what was probably the first suicide attack of the war off the coast of New Guinea in May 1944.

The prototype Ki-45 was first flown in January 1939 with license-produced Bristol Mercury engines, these were eventually switched in favor of the Ha-25 in later prototypes. The Ki-45-KAI eventually entered production in May 1941 and was produced in a number of subvariants beginning with the Ki-45-KAIa which was the standard heavy fighter. Ground attack and maritime strike aircraft were known as the Ki-45-KAIb with a powerful 37-mm cannon as well as the Ki-45-KAId which added two additional 20-mm guns in the nose. Finally, the Ki-45-KAIc was the dedicated night fighter with oblique 20-mm armament similer to its German counterparts.