The story of the forty-seven ronin—a group of samurai who fall from that status when their lord is forced to commit ritual suicide and then take vengeance on the nobleman responsible for his death, realizing that the act will doom them as well—is apparently a Japanese classic. Based on an actual incident that occurred in the early eighteenth century, it was later taken up in literary circles, including a goodly number of plays, and has been the subject of numerous films and television adaptations. In the process it’s been much tinkered with over the years, so that fact that this big-budget Hollywoodized take on it adds tweaks of its own should come as no surprise.

The first of the additions are the CGI effects that are considered obligatory for such action fare nowadays, which scripters Chris Morgan and Hossein Amini manage to insert by inventing a femme fatale figure—an actual witch (Rinko Kikuchi)—who becomes the confidante of the wicked lord Kira (Tadanobu Asano) who plots the fall of Lord Asano (Min Tanaka) so that the Shogun (Cary-Hiroyuko Tagawa) will reward him not only with Asano’s lands but also with the hand of the dead man’s lovely daughter Mika (Kou Shibasaki). The witch is a shapeshifter: at the beginning she prefers to appear as an attractive white wolf, but later on she prefers to morph into a slithering mass of ooze, often with hair that slinks out like tendrils seeking a victim. Toward the close she even morphs into a huge dragon. And she concocts beasties, too. A giant rhino-type thing with three pairs of eyes tears up the forest in an early scene, and to poison Asano—and make him hypnotically attack Kira, bringing about his own demise—she fashions an iridescent spider from thin air. She’s also presumably the source of the seven-foot silver samurai fighter who’s Kira’s champion, and looks as if it had wandered in from the conclusion of “The Wolverine.” Some of this—especially the spider—is very cool, but you wonder why she has to bother with all this middle-man stuff if she’s so powerful. Silly question: because it allows the special effects crew to run riot.

But that’s not enough. The plot has to make room for not only a romantic subplot but a western star. So Morgan and Amini shoehorn a new character into the mix—a “halfbreed” named Kai (Keanu Reeves), who’s described as the unexpected result of a one-night stand between a peasant girl and an English sailor, and who spent his childhood deep in the forest with a group of outcasts who might be demons, but escaped and was taken in by Asano; though treated as a servant, he and Mika feel in love. In this telling, Kai really replaces the story’s usual hero Oishi (Hiroyuki Sanada), the leader of the disgraced ronin, as the hero. It’s Kai who actually becomes the sparkplug of the band’s action against Kira, in the process earning the respect of his fellow fighters, who had always dismissed him as a mere underling, and often worse than that. And it’s he who, in the end, has to deal with the witch, while Oishi merely takes out the human Kira.

Curiously, what Kai’s story reminded this reviewer of more than anything else was Henry Hathaway’s 1954 take on Hal Foster’s comic strip “Prince Valiant,” the one with young Robert Wagner wearing a ridiculous pageboy haircut. Reeves doesn’t wear a pageboy—he’s got long hair and a gloomy-looking beard instead—but like Valiant he’s disgraced when he steps into a knight’s armor to fight in a tournament, and one can imagine Valiant fighting a dragon, though Wagner didn’t. What’s most important is that “47 Ronin,” like Hathaway’s picture, has a fundamentally juvenile mentality. The Japanese tale, which was essentially a serious commentary on the samurai bushido code, is turned into a cartoonish take on the subject, much as “Prince Valiant” treated the whole Arthurian legend. (In that connection it’s surprising that the picture has so little humor, apart from what’s afforded by Takato Yonemoto as the chubbiest ronin.)

And of course the presence of Reeves doesn’t help. He tries to fit in with the distinguished Japanese actors who surround him, but his typically glum expression and flat line delivery (especially when contrasted with the slightly British tones of the actor who plays Kai in his younger days) feel completely out of place. It’s a pity that he takes so much of the attention from Sanada who, one suspects, could have made far more of Oishi—the hero of the original story—especially if the explanation for how he persuaded Kira to dismiss him as a danger (he acted as though he’d become a drunken has-been) had been retained, rather than having him and his forty-seven colleagues be the survivors of an earlier defeat by the Lord’s men whose reappearance comes as a shock. (“We will be ghosts,” Kai explains, “which will work to our advantage.”) On the other hand, it would have been wise to ratchet down Asano and Kikuchi a trifle, even if within this context their lip-smacking villainy is to be expected.

“47 Ronin” is director Carl Rinsch’s first feature, and in the elegance of its compositions and visual flair it shows his background in commercials, though cinematographer John Mathieson obviously had a hand in them as well. One can’t hold Rinsch fully responsible for the result, however, as reports suggest he was removed by the studio during the editing process (credited to Stuart Baird), when—it’s reported—retakes (including the final dragon fight) were added, supposedly ballooning the cost to something north of $200 million. A lot of that money is on the screen in sets, costumes, and crowds (the production designer was Jan Roelfs, the supervising art director Gary Freeman, the set decorator Elli Griff and the costume designer Penny Rose)—as well as the effects (though the rhino creature frankly looks a bit cheesy); but it can hardly be denied that this is a major example of budget bloat of astronomical proportions.

So in their quest to give the classic story international appeal, the makers have turned “47 Ronin” into an extravagant live-action comic book with a distinctly juvenile sensibility. That makes the decision to retain the ending, which by western standards has a tragic dimension (as was the case with “The Magnificent Seven,” derived from “The Seven Samurai”) gutsy. But it doesn’t save the picture from being a serious miscalculation, which will probably also go down in cinema history as a financial debacle.