Song-class submarines of China’s People’s Liberation Army Navy (PLAN).
KUALA LUMPUR – The Japanese Ministry of Defense detected a Chinese submarine operating in the contiguous zone of Japan’s southern islands, they announced in a Sept. 12 press release, and the Japan Maritime Self Defense Force (JMSDF) air and naval units are maintaining surveillance on the submarine.
The submarine had been spotted by the JMSDF in the morning of Sept. 10 moving in a northwest direction while in the eastern waters...
https://news.usni.org/2021/09/13/japanese-military-spots-chinese-sub-near-southern-islands