Takuan encourages Musashi to be more serious about training and not throw away his life so easily, but Musashi still has a lot to learn. He splits up with Takuan and goes to visit the Hōzōin temple for its famous spear technique. Gion Toji, the Yoshioka school's assassin who seeks to kill Musashi, arrives at the temple first. He cuts both hands off a monk who challenges him and proclaims that he will come back everyday and do the same to others until he finds Musashi, throwing the temple into turmoil and unease.

Musashi appears at the temple the next day and picks a fight with Agon, one of the higher-level monks. Musashi seeks In'ei, the old and legendary master of the school, whom he does not know has retired. Agon recognizes that this must be Musashi and, seeking both to end the turmoil that Toji has caused and defend Hōzōin's name, he fights Musashi. At one point, Musashi finds himself without a sword but he manages to end the fight by breaking Agon's nose.

Gion Toji then challenges Musashi, but before they can begin, Inshun, the new master of the school and a child prodigy at the spear, breaks up the fight, wanting to battle Musashi himself. Toji backs off and Musashi has an all-out battle with Inshun. Musashi becomes tired and distraught and flees from Inshun badly beaten. He winds up later in the care of In'ei, the same monk and spearmaster he had journeyed to Hōzōin to fight. The elderly In'ei feels that while Inshun, his greatest student, has brilliantly mastered the physical art of spear fighting, he has not mastered himself and his soul. He believes Inshun needs a powerful rival to do this and trains Musashi so that he can be that rival.

In the end, Musashi gets a second battle with Inshun, with only In'ei and Agon as witnesses. Having learned a lot from his training about himself and his demons, Musashi overpowers Inshun's spirit. He manages to dodge Inshun's attack and knocks him down with a strike to the head from his own self-carved sword; after this, he reverts to his savage self and starts beating the ground and the fallen Inshun with his sword repeatedly. Both Musashi and Inshun are treated for any injuries at the Hōzōin Temple, after which Musashi was issued finer robes and a pair of swords. They leave with the vow of trying not to kill each other the next time they meet.