The were a class of ships in the service of the Imperial Japanese Navy during World War II. 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 four ships of the Shimushu class would provide the foundation for the five following classes of 171 Japanese Kaibōkan-type escort ships.