Its sole operator is the Japan Air Self-Defense Force (JASDF), in part due to historic restrictions on the exporting of military hardware.

In addition to its primary training mission, the T-4 has been used by the JASDF's Blue Impulse aerobatic team as well as liaison duties with most fighter units.

[2] The MT-X program had been launched to procure a replacement for the aging Lockheed T-33[3] and Fuji T-1 jet trainer aircraft then in service in the Japan Air Self Defense Force (JASDF).

[6] Kawasaki's design team was headed by the aeronautics engineer Kohki Isozaki, as well as working in close conjunction with planners at the Japanese defense agency.

[8] Reportedly, the selection of a twin-engine configuration for the trainer was one of the easiest decisions taken, being made not just for engine power but from a high priority being placed upon safety.

[2] A robust, damage-tolerant and long-lived structure was also specified for the trainer; in order to achieve this, it was decided to make limited use of composite materials in the form of carbon fiber and kevlar in areas such as the radome and elements of the rear wing, tail unit, and undercarriage.

Reportedly, test pilots of the Air Proving Wing who flew the XT-4 observed the type to have greater subsonic manoeuvrability than the McDonnell Douglas F-15 Eagle, an agile aerial supremacy fighter.

Specifically, the T-4 possessed a lower wing loading and 20 per cent greater thrust-to-weight ratio than either of these aircraft, easily permitting an initial climb to altitude rate of 3,000 m (10,000 ft) per minute.

[21] While no combat-orientated model of the aircraft has been developed to date, the standard T-4 features three hard points, enabling the installation of various air-to-air missiles, bombs, and a gun pod.

[8] Its structure has sufficient strength to enable high-g manoeuvres, being rated to perform instantaneous dives of 7.33g when flown in a clean configuration.