細川忠興
Apparently, the young Musashi, at the time, around 29 years old, heard of Sasaki's fame and asked Lord Hosokawa Tadaoki, through an intermediary, Nagaoka Sado Okinaga, a principal vassal of Tadaoki, to arrange a duel. Tadaoki assented and set the time and place as 13 April 1612 on the comparatively remote island of Ganryujima of Funashima, the strait between Honshū and Kyūshū. The match was probably set in such a remote place because by this time Sasaki had acquired many students and disciples, and were Sasaki to lose, they would probably have attempted to kill Musashi.