South Korean businesses are increasingly acquiring real estate around the Maritime Self-Defense Force's base on Tsushima Island, arousing speculation that some of the purchases are related to espionage by Seoul.

Tsushima is situated in the Sea of Japan about 50 km from the Korean Peninsula and is administered by Nagasaki Prefecture in Kyushu.

In June 2008, a South Korean resort facility was opened on a lot adjacent to the MSDF base in charge of keeping tabs on the Tsushima Strait.