The Natsushio-class submarines were significantly smaller than the next generation Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese submarines, the Ōshio, and the Natsushio-class submarines were the development of the Hayashio-class submarine

Hayashio class submarine

Hayashio class submarine was the successor of the Oyashio, and the predecessor of the Natsushio-class submarine.-Boats:...

s. Also, Natsushio-class is one of the (coast-defence) hunter-killer submarine (SSK) of JMSDF. However, the JMSDF did not welcome the small submarines. Therefore, their successor was not built.

Boats

Project no.	Building no.	Pennant no.	Name	Laid down	Launched	Commissioned	Note
S116	8703	SS-523		5 December 1961	18 September 1962	29 June 1963	Decommissioned 20 March 1978, scrapped
	8704	SS-524		6 December 1961	14 December 1962	17 September 1963	Decommissioned 10 June 1980, scrapped