The Natsushio-class submarines were significantly smaller than the next generation Japanese submarines, the Ōshio, and the Natsushio-class submarines were the development of the Hayashio-class submarines. Also, Natsushio-class is one of the (coast-defence) hunter-killer submarine (SSK) of JMSDF. Construction of the two subs in the class was approved under the First Defense Buildup Program 1958-1960. However, the MSDF brass did not welcome the small submarines. Ongoing maneuvering regarding defense spending by the Ministry of Finance did not help matters. At the time, the Maritime Staff Office was trying to move the MSDF away from being a predominantly Green-water navy (due to politics and budgetary issues this would not begin to happen until the 1980s). Small coastal SSKs like the Natsushi