The Japanese called these ships Kaibōkan, "ocean defence ships", (Kai = sea, ocean, Bo = defence, Kan = ship), to denote a multi-purpose vessel. They were initially intended for patrol and fishery protection, minesweeping and as convoy escorts. The ships measured 77.72m (254.99feet) overall, with a beam of 9.1m (29.9feet) and a draft of 3.05m (10.01feet).[1] They displaced 860sp=usNaNsp=us at standard load and 1020sp=usNaNsp=us at deep load. The ships had two diesel engines, each driving one propeller shaft, which were rated at a total of 4200bhp for a speed of 19.7kn. The ships had a range of 8000nmi at a speed of .[2]
The main armament of the Shimushu class consisted of three Type 3 1201NaN1 guns in single mounts, one superfiring pair aft and one mount forward of the superstructure. They were built with four Type 96 251NaN1 anti-aircraft guns in two twin-gun mounts, but the total was increased to 15 guns by August 1943. A dozen depth charges were stowed aboard initially, but this was doubled in May 1942 when their minesweeping gear was removed.[2] The anti-submarine weaponry later rose to 60 depth charges with a Type 97 811NaN1 trench mortar and six depth charge throwers.
Like her sister ship, Hachijo spent most of her early career in the Kuriles escorting ships. On 19 February 1943, Hachijo barely missed meeting her doom when she was detached from escorting Akagane Maru to Attu in the morning. That evening, Akagane Maru ran into the heavy cruiser with two destroyers and was sunk.
On 7 July 1944 Hachijo was severely damaged in an air attack, taking damage to her hull and an auxiliary engine room was flooded. Hachijo survived the war and was scrapped on 30 April 1948.