It was a huge hit in Japan in 2001 and even got a limited theatrical release in America a few years later. It also got a sequel, similarly based on the novel series by Baku Yumemakura, as part of an Onmyoji boom that also gave the world a highly regarded manga, a light novel series and a 2006 anime series.
It's nothing special, though. Its folkore and traditional magic are nothing that hasn't appeared in lots of anime, while today its 2001 CGI special effects make it look like a straight-to-DVD cheapie.
It's a period fantasy set in the Heian era, i.e. amazing hats, while most of the cast are ostensibly historical characters. I suspect 10th century Japan didn't actually have wuxia, immortality, CGI demons or paper golems, though. The word "onmyoji" refers to traditional Japanese mysticism, based on Chinese principles and influenced by Taoism, Buddhism and Shintoism. Thus the Chinese kanji for "onmyoji" are the same as those for "Yin and Yang" in Chinese, while its magical paper seals that you'll see all the time in anime are basically the same as those in, say, Hong Kong Hopping Vampire films.
Its main sorceror is Abe no Seimei (921-1005), who's famous in Japan and has since been used as a character in many stories and films. His traditional nemesis, Ashiya Doman, is here too and portrayed by Hiroyuki Sanada (Ringu, The Last Samurai, The Wolverine, Lost season six and a stint at the RSC). Seimei in this film uses LOTS of magic. It's like 10th century Japanese electricity or something. He has magical assistants to help him around the house who look human but are really paper dolls, for instance.
Anyway, the storyline is superficial. The first half-hour made my eyelids heavy, although stuff started happening later. Abe no Seimei makes a friend, Hiromasa (Hideaki Ito) and tries not very hard to stop Doman from doing bad stuff. None of this gets inside the characters and it's just a low-energy supernatural runaround. Later, though, Doman initiates vampire oni battle scenes and becomes a bwahahahaha-ing supervillain, which wakes up the audience even if it's hardly inspiring Hiroyuki Sanada to his finest work. (He's still one of the two actors here worth watching, though, and Sanada gets good again in the final Seimei-Doman confrontation.) There's quite a good scene with two dead people from 150 years ago and Seimei gets a fight scene where he flies through the air as if he's rehearsing for Crouching Tiger, Hidden Dragon.
I can imagine two ways of watching this film. The first is to treat it as silly effects-heavy period fantasy, like many Hong Kong flicks. In some ways, it resembles Hong Kong's cinema more than it does Japan's. Tomoko had heard this described as "a big Kadokawa film", i.e. bubblegum spectacle, which is reasonable enough since it was indeed made by Kadokawa.
It also has spooky horror-like elements, which are fun even if I'd have preferred to see the director going for them with more gusto. Japanese folklore can be nasty and this film has decapitations, flying body parts, wacky demons, etc.
The other way of watching this is to pay attention to the actors. That's mostly Mansai Nomura (Abe no Seimei) and Sanada, of course. Hideaki Ito commits a gaffe or two and never really convinced me that he was from the 10th century, although he's likeable enough in an everyman kind of way. I liked him in a certain character's death scene, though. Meanwhile there are some reaction shots that suggested that the film wasn't always being taken seriously, e.g. a non-reaction to a severed head, or the Emperor's panto-level overacting on ordering Seimei's execution.
Nomura's performance as Seimei is extraordinary, though. I don't mean extraordinarily good, although as it happens he won a Best Actor Blue Ribbon Award for it. No, it's just that he's made some eccentric characterisation choices. I was mesmerised, until, near the end, I decided I'd figured it out. Nomura's a famous stage actor in Japan, by the way, even though he has little international profile. Qualities in his performance here include:
1. An almost mask-like serenity and an ability to keep smiling at almost anything. He's not even fully human, since his mother was a fox spirit. (At one point, he and his sidekick Hiromasa reminded me of Doctor Who and a random companion.) He's a nice guy, obviously, and clearly a dude you want on your side, but he doesn't really care about things like the Emperor or the fate of Kyoto. Someone can get cut down with a sword in front of him and he'll still be looking like the Cheshire Cat.
It's possible to break that serenity, though, as we eventually learn. I like the subtleties with which Nomura shades that.
2. A strong enough gay reading that personally I'm convinced Nomura was deliberately using that in his performance, although Tomoko didn't agree with me on this and the film is, on the face of it, entirely heterosexual. For starters, imagine you're an actor picking up this script. You're playing a character who rejects all things traditionally masculine (e.g. power, sword fighting) and hangs out with a bunch of magically-created women patterned so closely on yourself that they often echo your dialogue. You don't care about anything and you'd happily let your arch-enemy take over Kyoto... until your boy friend Hiromasa's life is threatened, at which point you swing into action and even lose your extraordinary self-control. Not only do you cry over him, but you then go into denial about it and the film's last scene has Hiromasa teasing you about the fact that you were crying.
This will never be explained. Hiromasa isn't your long-lost brother or anything. It's just that you're just a free-spirited batchelor who appears to have fallen hard for the pretty boy whose plot role is indistinguishable from that of The Girlfriend. (Hiromasa does some sword-fighting and falls in love with a lady, but his relationship with Seimei and what happens to him to give Seimei dramatic scenes to play are what make him fundamentally the girlfriend.)
Oh, and there's an even more intense boy-on-boy pairing in Doman with Prince Sawara, which ends with Hiromasa being possessed by a girl from 150 years ago and seducing Sawara away from his new boyfriend. After that, the Doman-Seimei finale is similarly suggestive of slash fiction possibilities.
Put all that together and Nomura's chosen characterisation starts making a lot of sense. Yes, you can take a lot from his half-human nature and unknowable age. If his mother was a half-spirit, then it's not unreasonable for him to be giving people foxy looks. However I personally think of Nomura's performance as the 10th century equivalent of a flaming queen, camping his way through a historical costume drama as a character who today would probably be dancing to Abba in a jockstrap and sequinned ostrich feathers. That's entirely my personal interpretation, I hasten to say. None of this even occurred to Tomoko. He conforms to no modern homosexual stereotype... but once the idea had got into my head, nothing would make it leave.
I think this is great, by the way. It's subtext that creates a human layer in what otherwise, I'm afraid, feels like a fairly unremarkable film. Lots of spooky magical stuff, some sword fighting, demons, spells and so on, but a cast who are mostly types rather than fleshed-out characters. If it weren't for my suggested gay subtext, then the nearest we'd get to a three-dimensional character would be Sawada's Doman.
I wasn't enamoured of this film in its early stages, but it eventually picks up to be an acceptable time-waster. The special effects come thick and fast and I'm prepared to give it the benefit of the doubt by assuming that it looked impressive in 2001. Today, of course, it looks like a Doctor Who era that never happened. (Doctor Who's never been this riddled with such cheap-looking CGI, although I'm sure we'd have had episodes like this if it weren't for the 1989-2005 hiatus.) The horror elements are fun, if generally mishandled. The Japanese folklore is entertaining and would probably seem really weird if you're not an anime fan and familiar with it all already. The main attraction, though, is Nomura's weird, smug take on Seimei. He's making bold choices. He bewildered me for a while, but I applaud that.