細川忠興
In 1611, Musashi began practicing zazen at the Myōshin-ji temple, where he met Nagaoka Sado, vassal to Hosokawa Tadaoki; Tadaoki was a powerful lord who had received the Kumamoto Domain in west-central Kyūshū after the Battle of Sekigahara. Munisai had moved to northern Kyūshū and became Tadaoki's teacher, leading to the possibility that Munisai introduced Musashi to Sasaki Kojirō, another guest of the Hosokawa clan at the time. Somehow, a duel was proposed between the two; in some versions, Nagaoka proposed the duel, in others with Kojirō proposed it out of rivalry or jealously. Tokitsu believes that the duel was politically motivated, as a matter of consolidating Tadaoki's control over his fief.