It's quirky, stylistically unique, and manages to be (slightly) informative without being boring. If you just want to pass the time with an idle amusement, it meets the role if you can handle the quirk factor and occasional divergences from the documentary's thesis (despite its brevity, there's an entire tangent on the history of equestrian warfare).
As a documentary. . . a three.
As a longtime fan of both Mamoru Oshii and the historical figure of Miyamoto Musashi, I couldn't help but wonder if this was meant as satire. Indeed, it bears none of the classic marks associated with Oshii; it actually bears marks quite contrary to what you'd expect from him. The quirky and light-hearted presentation is a polar contrast from his usual dark and grandiose style.
But, beyond stylistic directorial anomalies, what actually ruins this documentary, making it an utter disgrace to the personage it aims to (or claims to) homage, is the fact that it fails so horribly as a documentary. Despite the early claim that the viewer will be presented with a true look at Miyomoto Musashi, that peers through the legends and tall-tales that have sprung up over the centuries, historically documented events of great import in the life of Japan's most well-known swordsman are glossed over or ignored altogether. What is presented in the place of historic fact?
Tendentious propaganda.
The documentary seeks to assail the viewer, repeatedly, with the completely groundless presupposition that Miyomoto Musashi was tortured and driven entirely by a burning ambition to attain rank and command in battle, and to become a "Great Man." The documentary even ends on this note. The reasonings for this theory (which would be acceptable if it was presented as a theory and not as a cold, hard assertion of uncontested fact) are vague and slight, relying on things so miniscule as Musashi's writing in the Gorin no Sho (his treatise on martial arts, and bible to modern practitioners of the budo) that small battles can be compared to large battles, and an insistence that his (evidently) preferred stance (contrary to his writings) was most effective against mounted opponents. . . evidently proof that Musashi harbored an obsession with horses and horse warriors.
The problem with this is that the documentary doesn't even tell us where it acquired this "preferred" stance in order to scrutinize its efficacy; whether it was taken from extant scrolls passed down in the Niten Ichi Ryu, (the school of swordsmanship Musashi founded) written generations after his death, or (most likely) from popular fiction, movies with fight choreography aimed at flashy visuals rather than historical accuracy.
It completely neglects to mention that Musashi preferred independence and freedom to the point that he even (tried to) refuse the honor of being brought into a daimyo's castle while dying, preferring to remain in the cave that he made his home in his last years, or that in the Dokkodo, his 21 precepts on the way of the warrior, he shunned personal ambition. In fact, Musashi: the Dream of the Last Samurai goes so far as to call him a hypocrite by insisting so profusely that he did not personally hold to his own teachings in heart. But then, despite taking vaguely based assumptions as fact, it does go so far as to question the authenticity of his writings altogether (if not directly).
Also, another grating factor: there is a point where it is stressed that the common belief that Musashi was a practitioner of zen meditation is completely false (despite some possible zen allusions in his personally documented fighting style), insisting that because Musashi's writing style is direct and unpoetic, he could not possibly have had any zen influence, because zen is associated with paradoxical koans. While it cannot be proven one way or the other whether Musashi was a zazen practitioner, this absurd logic just shows us that the writer knew as little about zen as he did about Miyamoto Musashi, as he doesn't bother mentioning that the application of the popular style now associated with zen wasn't applied to the transmission of Japanese swordsmanship ("your sword must be the water reflecting the moon while gazing at the mountain over a field filled with poppies on a clear winter night" nonsense) until a few generations later, after the actual need for swordplay had completely died out, making it more aesthetic than practical.
So, in conclusion, this so-called "documentary" neglects everything of import about Miyamoto Musashi, blatantly ignoring or glossing over a lifetime given to the "mastery of all things," stressing with utmost assertion that a man who traveled extensively, trained diligently, sculpted, painted, kept the personal company of high ranking geisha and fellow men of great repute, assisted in the architectural design of castle-towns, won over sixty duels and founded a sword school, being remembered centuries later as a "Great Man," was, in truth, just compensating for the fact he never got to fight on a horse.
If you are interested in Miyamoto Musashi, William Scott Wilson's The Lone Samurai: The Life of Miyamoto Musashi is probably the best English resource I've come across. Musashi: The Dream of The Last Samurai is the worst.
