This class consists of MYOKEN, MYOHO, MYOKO and MYOGI MARUs. MYOKEN MARU was completed as a cargo ship in 1938 for for Nippon Yusen Kisen (NYK Line), K.K., Tokyo. In 1939, she was transferred to Toa Kaiun (East China Shipping Co., Ltd.) of Shanghai, a Japanese entity.
In 1941, she was requisitioned by the IJN and converted to a gunboat. On 24 January '42 MYOKEN MARU was torpedoed and sunk by an American submarine off Kendari,
Celebes, Dutch East Indies.

Sister MYOHO MARU was completed as a cargo ship in 1939 also for Nippon Yusen Kisen and was transferred to Toa Kaiun (East China Shipping Co.) that same year. She was requisitioned by the IJA and converted to a troop transport. On 19 January '43, MYOHO MARU was torpedoed and sunk by an American submarine

The two other sisters in this class of 4 ships were MYOKO MARU and MYOGI MARU. Both were completed in 1939 and transferred the same year to the newly created Toa Kaiun entity. Like MYOHO MARU both were requisitioned by the IJA and sunk in the war. MYOKO MARU was bombed and sunk off Lae 8 Jan 1943 and MYOGI MARU was bombed and sunk in Manila on 13 November 1944. Neither of these ships have TROMs written for them presently. MYOKO MARU needs to be distinguished from the larger ship of the same name found under Zatsuyosen (IJN Transports).