The Soukou-Tei No.4 (also known as the AB-4) was the first production model Soukou-Tei/AB-Tei which was ready by 1933. After the successful operations of the earlier AB-1 'Sakigake' and AB-2 'Kachidoki', the armament was updated with Japan's newest equipment switching the machine guns to dual 7.7 mm instead of 6.5 mm and upgrading the 37 mm Type 11 infantry gun to the 57 mm Type 97 tank gun. The armour was more efficiently welded which provided the same or better armour values with reduced weight which, along with the conversion to a diesel engine, also allowed it to reach higher speeds than its predecessors.

It was introduced in Update 1.89 "Imperial Navy". The AB-4 plays similarly to its earlier prototype the AB-1 'Sakigake' but is improved in all departments. The AB-4 has better performance, mobility, and firepower than its predecessor, but it still suffers from the limitations of its design for open sea combat. The AB-4 is equipped with two 7.7 mm Type 89 'special' machine guns in dual mounts and a 57 mm Type 97 tank gun that is also used on the I-Go and Chi-Ha. The AB-4 can operate more independently than the AB-1, but it may still benefit from the assistance of other vessels for towing or escorting. The 7.7 mm machine guns can deal considerable damage to lightly armoured targets, such as patrol boats and aircraft, but have limited range. The 57 mm tank gun can deal excellent damage, but it has accuracy and velocity issues that make it difficult to hit fast-moving or distant enemies.