Laid down by Mitsubishi Shipbuilding, Nagasaki, Japan for account of the Osaka Shosen Kaiska (OSK) Line as a passenger annex cargo ship with yard number 457 on 16 May 1929, launched on 19 November 1929, completed on 15 May 1930, begun her maiden voyage on 1 June 1930, purchased by the Japanese navy on 8 October 1940, started by Kore Navy Yard with converting her into a transport on 19 October 1940, classified as the transport Rio Maru serving in the Sasebo naval District, conversion completed on 30 November 1940, classified to be a submarine tender, converted into such a tender by Harima‘s shipyard, completed on 7 May 1941, badly damaged by a torpedo fired by the American submarine USS Swordfish in the Balabac Strait, north of Borneo, Dutch East Indies, dry-docked and repaired in the Seletar’s No. 1 Shipyard at Singapore (the former King George V Graving Dock), in 1943 serving as transport, hit during an American air attack east of Uman Island and sunk after midnight in the Truk Lagoon and stricken on 31 March 1944. Called a Buenos Aires class ocean liner. Gross register tonnage 9.627 tons, dimensions 140,5 x 18,9 x 12 metres and passenger accommodation for 1.140 persons. Peed 17,1 knots. Made several voyages towards Brazil with emigrants on board. Armed with 2-2,5cm Type 96 dual anti aircraft guns as a transport and as a submarine tender 4-15cm/5.9” guns. As submarine tender fitted out with an anti-magnetic mine degaussing coil, range under, torpedo and depth charger hangar and medical facility.
