The Shōkai Maru-class high-powered tugboat (照海丸型強力曳船,, Shōkai Maru-gata kyōryoku eisen) was a class of gunboat of the Imperial Japanese Army, serving during World War II. The IJA official designation was high-powered tugboat, however, they did not have any towing facilities. They were actually gunboat and escort ships. Many records were lost after the Surrender of Japan.

• 20 April 1938; completed at Ōsaka Iron Works, Sakurajima Factory.
• Hereafter, her record was not left to documents.

• 27 February 1939; completed at Ōsaka Iron Works, Sakurajima Factory.
• 20 to 26 October 1944; escort operation for Harukaze Convoy (Manila - Kaohsiung).^[5]
• 22 to 27 November 1944; escort operation for TaKa-206 Convoy (Keelung - Naha).^[6]
• Survived war in Kushigahama; later rebuilt as short-range passenger at Mitsubishi Heavy Industries, Hiroshima shipyard.^[3]
• 1 May 1946; transferred to Japanese National Railways (later converted to training ship).^[3]
• 1 September 1948; transferred to Japan Maritime Safety Agency as patrol boat (PB-31, later PS-31).^[7]
• 23 June 1951; retired.^[7]

• Monthly Ships of the World, "Kaijinsha"., (Japan)
  • No. 506, February 1996
  • No. 613, Special issue "All ships of Japan Coast Guard 1948–2003", July 2003
• Shinshichirō Komamiya, The Wartime Convoy Histories, "Shuppan Kyōdōsha". Archived from the original on 2011-07-22. Retrieved 2011-12-15. (Japan), October 1987
• Tatsuo Furukawa, Wake of train ferry 100-year (2nd issue), "Seizando-Shoten". Archived from the original on 2009-04-17. (Japan), June 2001, ISBN 4-425-92141-0
• 100 year History of Hitachi Zōsen, Hitachi Zōsen Corporation, March 1985
• Policy and Legal Affairs Division-Japan Maritime Safety Agency (JMSA), 30 year History of Japan Maritime Safety Agency, Japan Maritime Safety Agency, May 1979