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.

The famed ninja Yagyu Jubei fights to suppress a coup d’etat plotted against Tokugawa Shogunate.

A wave of terror is threatening to unseat Shogun Yoshimune. Police stations are erupting into flames, convicts escaping from prison, houses robbed and vandalized, streets teeming with panicked citizens. Is Ijyuin Tanomo, highly-placed official of Owari clan, secretly using deadly ninja to foment riot and rebellion? Narumiya Shinbei, a lone samurai spy adept at ninjutsu must uncover the hidden hand orchestrating these shocking crimes. Shinbei enlists a small band of dedicated ninja to lay siege to the enemy’s stronghold, where his own sister works as an undercover agent. Now, ninja must fight ninja in a last desperate battle to save the shogunate.