China, Russia navy ships jointly sail through Japan strait
TOKYO, Oct 19 (Reuters) - A group of 10 naval vessels from China and Russia sailed through a strait separating Japan's main island and its northern island of Hokkaido on Monday, the Japanese government said, adding that it is closely watching such activities.
It was the first time Japan has confirmed the passage of Chinese and Russian naval vessels sailing together through the Tsugaru Strait, which separates the Sea of Japan from the Pacific.
While the strait is regarded as international waters, Japan's ties with China have long been plagued by conflicting claims over a group of tiny East China Sea islets. Tokyo has a territorial dispute with Moscow, as well.
https://www.reuters.com/world/asia-pacific/china-russia-navy-ships-jointly-sail-through-japan-strait-2021-10-19/
Tokyo also has a territorial dispute with South Korea concerning Dokdo roughly in the center of the East Sea/Sea of Japan.