The class was also referred to by internal Japanese documents as the "Modified A-class" coastal defense vessel (甲型海防艦, Kō-gata kaibōkan).

The Shimushu-class kaibōkan, as with the Chidori-class torpedo boat, was a consequence of the 1930 London Naval Treaty, which placed limitations on the total destroyer tonnage the Imperial Japanese Navy was permitted.

Immediately before the start of then Pacific War, the Imperial Japanese Navy suddenly decided to give more priority to convoy escorts, possibly in light of the ongoing successes of German U-boats against British shipping in the Atlantic.

The ships had two diesel engines, each driving one propeller shaft, which were rated at a total of 4,200 brake horsepower (3,100 kW) for a speed of 19.7 knots (36.5 km/h; 22.7 mph).

The ships had a range of 8,000 nautical miles (15,000 km; 9,200 mi) at a speed of 16 knots (30 km/h; 18 mph).

A Type 97 81-millimeter (3.2 in) trench mortar was also installed front of the bridge[3] The Etorofu class proved to be an inadequate design by the time the final units entered service in 1944.