In 1938, TATSUWA MARU was completed as a 6,335-ton cargo ship for Tatsuuma Kisen, K. K. In May '45, she struck a mine, probably laid by USAAF B-29 bombers, and sank in the waters off Shimonoseki.TATSUHO MARU was sunk by an American submarine off Keelung, Formosa in Aug '42. TATSUHARU and TATSUMIYA MARUs began conversion to minelayers in '41. TATSUHARU MARU was reconverted to an auxiliary transport in late '42, TATSUMIYA MARU was bombed and beached off Maizuru in Jul '45. In late '42, she too was reconverted to an auxiliary transport. Both TATSUMIYA and TATSUHARU MARUs survived the war. They were were scrapped in '68 and '70 respectively.