Inspired by the Grille series of self-propelled artillery vehicles developed by Nazi Germany during World War II, wherein a 15 cm sIG 33 infantry support gun was mounted on a tracked chassis, engineers at the Army Technical Bureau resolved to do the same.

[3] On to this platform, a Type 38 150 mm howitzer[4] based on a design by the German arms-manufacturer Krupp was mounted, but dated from 1905 and had been withdrawn from service as being obsolete in 1942.

Other design issues included the fact that although the gun crew was protected by a gun shield with armor thickness of 25 mm at the front, the shield with armor thickness of 12 mm only extended a very short distance on the sides; leaving the rest of the sides and back exposed.

In addition, the Ho-Ro did not have any secondary armament, such as a machine-gun, making it vulnerable to close combat.

[7] The Type 4 Ho-Ro was rushed into service, deployed and saw combat as part of the 2nd Tank Division with the Japanese Fourteenth Area Army during the Philippines Campaign in the last year of World War II.