Miyamoto Musashi IV: The Duel at Ichijo-ji Temple (1964)

In the fourth installment, Musashi's potentially greatest opponent Kojiro jumps in and out of the story at the oddest and most coincidental moments. As his great love Otsu has succumbed to madness. Musashi then sets off to beat the functionaries of a treacherous clan in an arranged duel. 73 against one. Boastful Kojiro watches, secure in the knowledge that only he is a worthy opponent.