- Green: Outstanding
- Yellow: Above Average
- Since the Luck Stat is difficult to modernize, it is listed as Base(Max).
- DEs cannot replace DDs in most of the ship type specific applications, unless otherwise specified.
- It has been found that, in several specific situations, for instance, in the formation of a Transportation Escort combined fleet, DEs are allowed to substitute DDs to meet the required minimal amount of DDs in the fleet. (Does not work for CTF/STF)
- It has also been found that DEs can replace other ship types in some specific expeditions.
- DEs only require a 60 displayed ASW value to perform OASW, as opposed to 100 for other ship classes.
- All implemented DEs have a slow speed, and thus cannot be used in branching rules that require a fast fleet.
- Unlike destroyers, they cannot equip Torpedoes, Turbines, Engines, Star shells, Searchlights, or Drums. They also have no torpedo stats, making them incapable of performing torpedo strikes, and cannot increase their speed by using turbine/engine combination.
- The plan to implement this ship class has existed since 2013, when the game started, according to the quarterly book 艦これ鎮守府生活のすゝめVol.1 released at the time. Players were told to be patient about their implementation since they were for the final phase of the war, despite stating that they want to release them as soon as possible. The ship class was ultimately implemented in May 2017, during Spring Event of that year.
Developed originally as fishery protection ships, with a secondary minesweeping and tertiary convoy escort wartime function, the Shimushu class coastal defence ships (Kaibōkan) became during the war the template for the main type of oceanic convoy escorts built by the IJN. These ships were initially conceived in the early 1930s, a resurgent Russian naval presence in the Far East resulted in a number of incidents involving Japanese fisheries in disputed waters, they were consistent with the unlimited category (Article 8) of the London Naval Treaty of 1930 that allowed to build ships like the British sloops, French avisos and the American Erie class patrol gunboats, but they were effectively authorised and built only with the 1937 naval programme, after Japan had left the Treaty system and the Second London Naval Treaty had removed those quantitative limitations that justified the introduction of an unlimited category.
Originally coastal defence ship was a classification used for obsolete battleships and cruisers deemed unfit for first line duties and assigned to coastal defence, it became a separate classification that included only the new escorts in July 1942, the surviving obsolete armoured cruisers were reclassified as heavy cruisers; the new classification was also moved from the Gunkan sub-group, which included main combatants like battleships, cruisers, carriers, etc. to the baseline Kantei group, which included destroyers, submarines, torpedo boats, etc.
Coastal defence ships are divided into six classes: Shimushu, Etorofu, Mikura, Ukuru, No.1 and No.2. Some authors rate the Hiburi class, which were hybrids between the Mikura and Ukuru built only by Hitachi, as a separate class, but others consider them to be part of the Ukuru class, officially they were part of the Mikura class. The official classification divided them into the following types:
Type A: Shimushu, Etorofu, Mikura, Ukuru
Type C: No.1
Type D. No.2
but as designed they had been originally divided into:
Type A: Etorofu
Tybe B: Mikura
Modified Type B: Ukuru
Type C: No.1
Type D: No.2
Shimushu class as a prototype had not been designed as part of any group, even though it was later retro-actively assigned to the Type A in the official classification.
The lack of an ASW emphasis in the Shimushu class can be evidenced from the limited depth charge stowage (12, increased to 24 since May 1942 and 60 since Autumn 1943) and the lack of sonar until Autumn 1942, coastal defence ships became genuine, purpose-built, convoy escorts only with the Mikura class, that was fitted with sonar since the beginning and carried 120 depth charges, albeit the minesweeping gear was dropped from the plans only with the Ukuru class. Mass production wasn't attempted until the Ukuru class and the Type C&D, which extensively employed welding and pre-fabrication.
During WWII the coastal defence ship classification was also used for the two former Chinese light cruisers Ning Hai and Ping Hai, in late 1943 the IJN decided to rebuild the two idle ships into escorts with a radically altered superstructure and armament analogous to the Type C&D kaibokan, they were respectively renamed Iaoshima and Isoshima. These relatively large ships were also supposed to serve as tenders for aircraft bases, for this purpose they were equipped with a crane on the mainmast, trucks, one daihatsu (14-m) and one shohatsu (10-m) landing craft. Yasoshima was re-rated as light cruiser for administrative reasons on 25 September 1944, it had been decided to appoint her as flagship for the newly organised First Transport Squadron, a role that required her to be rated as light cruiser.