In November 1950, they officially ordered the Fuji Precision Industries, one of the successors of disbanded Nakajima Aircraft Company, to design and produce a new gasoline engine for Tama.

)[2] Around ten people belonged to Tama's development team headed by the design manager Jiro Tanaka.

His assistant manager Takuya Himura, who would become the direct boss of Shinichiro Sakurai in October 1952, was in charge of the development of the Prince Sedan and other vehicles.

An evolution of the previous Tama Senior sedan, the front end resembled Russian cars of the era and the side had a European look.

The AISH-4 was released in February 1955 and was identical to the AISH-3 except for the engine, which was modified with a new cylinder head design that raised compression, increasing power to 52 hp (53 PS; 39 kW) and top speed to 115 km/h (71 mph).

In addition to the Sedan Standard there was also a Deluxe model, featuring extra equipment such as a radio, white sidewall tires, and an exterior sun visor.

This model was nearly identical to the AISH-5 except for the double wishbone independent front suspension which provided improved ride quality.

The grille was the same as the previous model, but the side strips were changed, now running horizontally the length of the car, except for a small V-shaped dip near the back of the rear doors.

Engine power increased again to 60 hp (61 PS; 45 kW) thanks to higher compression as improved quality fuel was becoming available in Japan.