It's actually directed by Hiroshi Inagaki.
The story starts out in the year 1600, towards the end of the Sengoku Period of Jidai Geki Japan. Takezo, a village commoner bent on winning fame and glory, wants to join up and fight in the shogunate wars. His buddy Matahachi is somewhat more reluctant to join up because he has something to keep him in the village, namely, his lovely fiancée Otsu. Takezo's enthusiasm wins his buddy over, though, and after extracting a promise from Otsu to wait for him, Matahachi joins up as well.
Unfortunately for Takezo and Matahachi, they pick the wrong side. Their army is routed at the Battle of Sekigahara, a decisive defeat that ends the shogunate wars. Takezo escapes, helping a badly wounded Matahachi along. They stumble through the woods until they find a cabin, which belongs to attractive Oko and Oko's even more attractive daughter Akemi. Three months pass as Matahachi recovers from an injured leg. Matahachi kisses Akemi but she rejects him. Akemi in turn tries to seduce Takezo but fails.
Takezo and Matahachi are surprised to find out that the seemingly sweet Oko and Akemi make their living by looting the bodies of dead samurai and selling what they find. And what's worse, bandits are coming to claim the treasures that the two women have stored up.
Samurai I: Musashi Miyamoto is loosely based on the novel series Musashi, which in turn is based on the life of a real guy, legendary sword fighter Miyamoto Musashi—who was also known as Takezo. It was the first film in a trilogy, followed up by Samurai II Duel At Ichijoji Temple and Samurai III: Duel at Ganryu Island.
- Absence Makes the Heart Go Yonder: Too much time away eventually leads Matahachi to forget about Otsu, first making a pass at Akemi and eventually marrying Oko.
- Armor-Piercing Question: Takuan gives Takezo a series of them so that he can shame him and capture him.Takuan: Are you trying to defeat yourself, too?Takuan: What about your relatives?Takezo (furiously): What relatives? They all hate me!Takuan: Some are suffering.Takezo: Hang them all! Better off dead, all of them!Takuan: Even the women?Takezo: (close to tears): Quiet!Takuan: And their children?
- As You Know: "Otsu, you're engaged to me, aren't you?"
- Badass Preacher: Takuan captures Takezo almost singlehandedly and even beats him when he has to.
- Batman Gambit: Takuan tricks Takezo into reforming by pretending that Otsu is waiting for him inside the castle, and then locking him away in the attic, forcing him to read from religious texts.
- Battle in the Rain: The battle of Sekigahara takes place in a driving rainstorm with Dramatic Thunder.
- Black Sheep: Takezo is the black sheep of the Shinmen family: rowdy, ambitious, full of challenge and desire. And his family all hate him.
- Break the Haughty: How Takuan eventually trains Takezo. The whole point of trussing him up and hanging him from a tree is to break his swagger and self-assurance so that a newly humbled Takezo will become a great samurai. It doesn't work the first time; Otsu frees him. When they go on the run, Takuan tricks Takezo into thinking that Otsu is waiting up for him inside the castle, and then locks him in the attic with only a bunch of books, which finally causes Takezo to surrender.
- But Now I Must Go: Despite Otsu's earnest pleas, Takezo, now newly christened "Musashi", leaves her behind, as he has to finish his samurai training.
- Celibate Hero: Takezo. He manages to rebuff the overt sexual advances of both Oko and her daughter Akemi. And at the end he leaves Otsu behind, because he has to finish his samurai training.
- Emotional Bruiser: Takezo, before he was refashioned into The Stoic Musashi.
- For Doom the Bell Tolls: An ominous bell can be heard on the soundtrack as Takezo and Matahachi go off to war. The ensuing battle goes badly.
- Glory Seeker: Why Takezo goes off to war, to win glory and fortune and escape his podunk village.
- Heroic RRoD: Otsu saves Takezo by cutting the rope that suspended him from the tree, but she cuts her hands in the process.
- Hero with Bad Publicity: Takezo is a good man at heart and is treated like a criminal due to being the victim of a travel ban for those on the losing side of the Battle of Sekigahara.
- Hot-Blooded: Takezo, for most of the movie, is fiery and temperamental.
- I Will Only Slow You Down: Otsu tells Takezo this as the posse is closing in, telling him that he should leave her behind and escape.
- Jidai Geki: End of the Sengoku period, including the battle of Sekigahara that ended it, and the beginning of the Edo period.
- Justified Criminal: Takezo killed a guard in self-defence while trying to get home, but only so he can survive and tell Otsu that Matahachi is alive.
- Kids Are Cruel: As a trussed-up Takezo hangs from a tree, the kids of the village wonder if he's dead. One says "Let's stone him and see", and they do.
- Manly Tears: Takezo cries a total of six times throughout the film, and the first five times it's less of a Single Tear and more like Inelegant Blubbering; notably he simultaneously weeps tears of gratitude after Otsu gets him down from the tree where he's been hanging, and tears of shame and remorse because all of the trouble he's caused ended up with her hands being cut badly.
- Master Swordsman: Takezo has a natural talent for swordplay, as shown in the scene where he fends off six bandits all by himself.
- Meaningful Rename: Takezo is christened "Musashi Miyamoto" at the end of the movie, having completed a major step in his samurai training.
- Not So Stoic: Musashi silently breaks down as he decides to leave Otsu.
- Rescue Romance: Takezo falls in love with Otsu properly after she rescues him from hanging from a massive tree.
- Rescue Sex: Averted. Oko is very turned on by watching Takezo fight off a half-dozen bandits single-handed and save her treasure box. She straight up says "Take me, Takezo!" and goes on to say that he can do anything he wants with her. He leaves.
- Riding into the Sunset: Walking, actually. But Musashi does this as he goes off to continue samurai training.
- Samurai: How did you guess?
- Sequel Hook: Musashi leaving while saying he has to complete his training. Two more films followed.
- Shirtless Scene: Or bare-chested, anyway. At the beginning, while he's a soldier, Takezo is working with the top of his tunic off.
- That Man Is Dead: Musashi tells Otsu that Takezo is gone, and there is only Musashi Miyamoto left.
- "Wanted!" Poster: The 17th century Japanese equivalent thereof, namely a handwritten poster saying that Takezo is a wanted man and a reward has been offered.
- Yamato Nadeshiko: Otsu, in contrast to Oko and Akemi, who are both schemers and kind of slutty to boot. She faithfully waits for Matahachi while he's off at war. After he cheats on her, she pledges herself to Takezo, helping him down from the tree at great personal risk, accompanying him in flight, and promising to be loyal to him forever.
- You Could Have Used Your Powers for Good: Takuan tells a trussed-up Takezo that he could have used his fighting spirit for good. This is despite the fact that Takezo's status as an outlaw happened because Takezo tried to do the right thing.