Almost everyone in Japan knows of the 17th-century swordsman Miyamoto Musashi and the legendary duel between him and his rival, Sasaki Kojirō. Musashi allegedly arrived at the duel purposefully late, wielding a wooden sword made out of an oar. Enraged by this disrespect, Kojirō lost his calm and was struck on the forehead, knocked unconscious, and was thus defeated (although accounts vary).

While there are numerous theories about the date of the event, there is one undoubted fact: that the duel took place on the small island of Ganryū-jima, located between Japan’s mainland (Honshū) and the Kyūshū region. Officially named Funa-jima, meaning "Boat Island," it was later nicknamed Ganryū-jima after the fighting style that Kojirō invented.

Originally a small island of merely 4 acres, Ganryū-jima is about 25 acres wide largely due to the landfill that Mitsubishi Heavy Industries—which owned most of the island until 2003—maintained. The island was home to about 30 families after World War II, but all of them abandoned Ganryū-jima during the 1970's, and it has been uninhabited since.

Most of the island has been maintained as a public park, and there is a pair of statues re-enacting and commemorating the duel between Musashi and Kojirō, immortalizing the legendary samurai.