The Imperial Japanese Navy (IJN) ordered 64 purpose-built cubmarine chasers in 1931 in preparation for war. The IJN augmented its fleet by requisitioning over 200 small Japanese merchant ships and capturing other nations’ patrol boats and minesweepers for conversion into auxiliary subchasers. These vessels were used in the Pacifics to patrol for U.S. submarines and to escort convoys of Japanese warships. No purpose-built subchasers were involved in the Battle of Saipan; however, some auxiliary subchasers were present at the time of the invasion. With its very sharp bow and sleek design, the ship closely matches the design of polar whaling ships conscripted by the IJN for auxiliary subchaser use.