Sourcing status: Disputed — this is a contested claim, not independently verified. Presented as a documented claim, not established fact.
Japanese Maritime Self-Defense Force escort destroyers reported simultaneous radar and visual returns of fast-moving objects over the Tsushima Strait. The case is referenced in retired-officer interviews and Japanese ufology literature; primary JMSDF records have not been released.
Sources
book: Yusuke Matsumura. Japanese UFO Studies (1974)