Kaiyo was built as the OSK liner Argentina Maru, completed in 1939. She was used as a troop transport from December 1941. The IJN bought her on 9 December 1942, converted her to an escort carrier and renamed her Kaiyo on 23 November 1943. She was used mainly as an aircraft transport, escort carrier and training ship.
On 10 February 1944, going from Palau to Truk, the submarine Permit made a night attack on her and missed. On 25 October 1944 she ferried a dozen transport aircraft to Keelung, Taiwan, and reached Kure on 2 November. Repeated air attacks badly damaged her in July 1945. She was towed to Beppu Bay and deliberately grounded to keep her from sinking. She was struck from the navy list on 20 November 1945 and scrapped in place from September 1946 to January 1948.
Sources: Wikipedia (ship articles), the Kure Maritime History Science Museum photograph records on Wikimedia Commons, and combinedfleet.com for the Chitose-class histories. No commanding-officer records were available for these ships.