This old man is credited with founding the Houzouin-Style Polearms Art. He is said to have studied under many different masters--he is even said to have studied the Shinkage-ryuu style of weapons arts taught byYagyuu Muneyoshi 柳生宗矩 (Sekishuusai).
In the game, his pupil, Houzouin Inshun 宝蔵院胤舜, has become too proud because he has gone undefeated for so long in the fighting competitions at the Koufuku Temple. Marume Nagayoshi 丸目長恵 starts a rumor that Musashi will come to face Inshun in an obvious attempt to lure the real Musashi out of hiding to investigate. He's got a message for him about Haruka 遥 and cautions about things that are yet to come. In'ei also seems to know what's going on. He mentions that "that Old Fox should be making his move pretty soon," alluding to the impending intervention of Tokugawa Ieyasu 徳川家康(The Mysterious Monk)."