The Japanese government lodged a formal protest with South Korea after a South Korean marine research vessel, identified as the ONNURI, conducted unauthorized marine research activities within Japan's territorial waters near the Takeshima Islands in Shimane Prefecture. On August 15, 2025, the vessel was observed deploying a wire-like object into the sea, an action confirmed by Japan's Ministry of Foreign Affairs. The incident occurred in the waters surrounding Takeshima, an area also claimed by South Korea under the name Dokdo. Japan's Ministry of Foreign Affairs publicly announced the protest on August 16, emphasizing the unauthorized nature of the survey and reaffirming Japan's territorial claims over the area.