The Shoki (Demon) soon proved itself to be the fastest Japanese Army fighter in service. However, the fighter was unable to intercept the Mitsubishi Ki-46 (Allied code name Dinah) high-altitude reconnaissance aircraft. (Very few Allied aircraft were able to intercept this excellent aircraft either). Consequently, work began immediately on a more powerful Model 2 version of the Shoki which would be even faster and have an even greater climb rate.

The Model 2 (Ki-44-II) was powered by the 1520 hp Nakajima Ha-109 radial, which was already in production as the Army Type 2 radial. The engine had the same diameter as that of the Ha-41, so the changes needed to incorporate it into the Shoki were minimal. The general configuration of the Model 2 was the same as the Model 1 version, but the undercarriage was strengthened. Five prototypes and three pre-production versions were built, and in August of 1942 the type replaced the Ki-44-I on Nakajima's production lines at Ota.

The Model 2 (Ki-44-II) became the major production version of the Shoki, and was built in three separate versions. The Ki-44-IIa was equipped with two fuselage-mounted 7.7-mm machine guns and two 12.7-mm machine guns in the wings. Only a relatively few examples of the IIa version were built. The major production version was the Ki-44-IIb (Model 2B). It carried a quartet of 12.7-mm machine guns, two in the fuselage and two in the wings. The Model IIc was armed with a quartet of 20-mm Ho-3 cannon and was intended primarily as a B-29 interceptor in defense of the Japanese home islands.

The Ki-44-II was first encountered by the Allies in the China, Burma, and Malaya theaters. Shoki fighters were also assigned the task of defending the vital oil fields at Palembang on Sumatra. Later, B-29 crews encountered the Tojo in their early sorties over the Japanese home islands. The Ki-44-IIc was particularly effective against the B-29, and was regarded as the toughest and most troublesome fighter that these bomber crews had to deal with at that stage in the war. Very few other Japanese fighters were capable of reaching the altitude at which the B-29 operated and still possess sufficient performance in order to intercept this bomber.

A few Ki-44-IIc fighters were armed with a pair of 12.7- mm machine guns and a pair of wing-mounted 40-mm Ho-301 cannon in an attempt to provide even more punch against the B-29. However, this cannon had a rather low muzzle velocity and was hence effective only at close ranges. A few other Ki-44-IIc fighters were fitted with a pair of 37-mm Ho-203 cannon with a somewhat higher muzzle velocity. However, both heavy cannon types were only moderately successful and saw only limited action.

By the time that production of the Shoki terminated in late 1944, 1167 Ki-44-II and III fighters had been built, a relatively small production number for a major fighter aircraft of the Second World War. At first, most Japanese pilots disliked the Shoki fighter because of its high landing speed and relatively poor maneuverability as compared to the more nimble aircraft that they were used to. However, they soon began to learn to take advantage of its high rate of climb and its excellent diving speed. When the B-29 raids against the Japanese homeland began, the Ki-44 was the only interceptor that the Army could field that was effective against this high-flying bomber. Against unescorted B-29s, the Ki-44 was considered as the toughest and most troublesome fighter available in Japan at that stage of the war. However, the Ki-44 was not without its faults. Its maneuverability was relatively poor and the aircraft was restricted against performing snap rolls, spins, stalls, and inverted flight at high speed. It was somewhat less forgiving of pilot mistakes than most of the more maneuverable Japanese fighters such as the Ki-43 Hayabusa. The armor protection for the pilot and the self-sealing tanks, although heavy in comparison with most previous Japanese fighters, was largely ineffective against Allied 50-cal machine guns. Many Shokis expended themselves in suicide ramming attacks against the long-ranging B-29s.