North Korea launched four strategic “Hwasal-2” cruise missiles from Kim Chaek City that fell into the Sea of Japan, according to state-run media publication Korean Central News Agency (KCNA).

Source: https://thehill.com/policy/defense/3872461-north-korea-flies-cruise-missiles-in-figure-eight-patterns-amid-us-allies-military-drills/

Officials say it likely splashed into the Sea of Japan off Hokkaido's Okushiri Island.

Source: https://newsonjapan.com/html/newsdesk/article/137961.php

Russia also tested submarine-launched missiles in the Sea of Japan last year.

Source: https://nypost.com/2023/03/28/russia-says-it-test-fired-anti-ship-missiles-in-sea-of-japan/

Scenarios of this kind might have been enacted or brought to the foreground in the recent joint exercises between China and Russia in the Sea of Japan.

Source: https://thediplomat.com/2023/08/what-is-russia-teaching-china-in-military-drills/

They will carry out sea and air convoys of ships, protect and defend groups of ships when moored in an unprotected estuary, and ensure the security of communications in the waters and airspace of the Sea of Japan, it added.

Source: https://en.mehrnews.com/news/203505/Russia-China-kick-off-joint-military-drills-in-sea-of-Japan