The original Ki-45 was a disappointment. Its Nakajima Ha-20 engines were underpowered and unreliable, the nacelles created drag, and performance fell short of the Army’s hopes. Rather than abandon the concept, Kawasaki’s team — led by Takeo Doi — reworked the aircraft almost completely: cleaner nacelles, better cooling, and progressively more powerful radials, first the Nakajima Ha-25 and finally the Mitsubishi Ha-102 of roughly 1,050–1,080 hp each. The rebuilt Ki-45 KAI (“modified”) flew in 1941 and reached squadrons in 1942. The lesson of the Toryu is that its success was not in the first design but in the willingness to fix it.

The definitive night fighter, the Ki-45 KAI Hei (Model C), mounted two 20 mm cannon obliquely in the upper fuselage, angled upward and forward. The tactic mirrored the Luftwaffe’s Schräge Musik installations: rather than chase a bomber into the fire of its tail and dorsal guns, the fighter formed up in the bomber’s blind spot below and behind, then raked the wings and fuselage from beneath. Against the B-29 — heavily defended and fast — getting into that position at night was the hard part, but when it worked the oblique guns were devastating. A nose-mounted 37 mm cannon gave the same aircraft a heavy forward punch.

When XX Bomber Command opened the strategic campaign against Japan in June 1944, the Army had no purpose-built night fighter ready — so it pressed the Toryu into the role. Dedicated night-fighter Sentai defended the industrial heartland, the Kanto plain and the approaches to Tokyo. Early results against B-29s flying at medium altitude were encouraging; the type’s top B-29 killer, Captain Isamu Kashiide of the 4th Sentai, was credited with a large personal tally (claims that, as with all such figures, exceed confirmed losses). But the plan depended on radar that never arrived in numbers, and as the B-29s switched tactics and pressed home low-level fire raids, the ageing Toryu was increasingly overwhelmed.

The Toryu was a wartime product of the Japanese state, built for the Imperial Japanese Army and never traded on any open market. No dependable flyaway unit price — in yen or dollar-equivalent — survives in the public record, and no credible cost-per-flight-hour figure exists for the type. Any precise number attached to a Ki-45 today should be treated as an estimate at best. What can be said is that the twin-engine Toryu was more expensive and material-hungry than a single-seat fighter, one reason Japan also fielded cheaper single-engine interceptors alongside it.