In 1941, the IJN had decided to build the bombing target ship Hakachi, with a speed under 20 knots (37 km/h).

However, what the IJN required was target ship which could emulate the higher speed of the Essex-class aircraft carriers and Iowa-class battleships.

The class specification given was therefore 33 knots, use of a destroyer hull, equipped with the Akizuki-class machinery, enabled this to be achieved and able to withstand a 10 kilogram bomb dropped from 4,000 m (13,000 ft) meters.

[3] However, the significant loss of destroyers between 1942 and 1944 together with delays in mass production of the Kaibōkan-escort ships caused Ōhama to be converted.

Thus rearmed for this escort role with many anti-aircraft arms and anti-submarine weapons, the lead ship Ōhama was completed on 10 January 1945.