In the early 1980s, the director Nagisa Oshima was preparing an adaptation of Laurens van der Post's novel The Seed and the Sower, set in a Japanese prisoner-of-war camp on Java during the Second World War. Oshima visited Robert Redford in New York to discuss the actor appearing in the film. "Redford said he had a lot of respect for my work," Oshima recounted in 1983, "but he didn't want to do this film. He thought the general American audience wouldn't understand it. I told him that though they might not understand at first, by the end they would. He responded by saying that if an American viewer doesn't understand a picture in the first 15 minutes, he gives up . . . But I am not interested in making films that can be understood in the first 15 minutes." Exit Redford, enter David Bowie, and hello Merry Christmas, Mr Lawrence.
As with other cross-cultural powwows in US hotel suites (Warren Beatty trying to charm Jean-Luc Godard into directing Bonnie and Clyde springs to mind), there is little one wouldn't give to have been a pretzel on the sideboard during that exchange. But what Redford's reticence failed to take into account is the magnetism that is one of Oshima's defining characteristics. He gives good seduction.
In deference to Redford's Law, let's consider the all-important opening 15 minutes of Empire of Passion (1978), a companion piece to Oshima's most notorious work, the 1976 erotic case-study In the Realm of the Senses. Empire of Passion, a supremely confident noir-horror that plays like The Postman Always Rings Twice rewritten by H P Lovecraft, begins with a rickshawman in a late-19th-century village suggesting to his wife that an ex-soldier has been hanging around because he's sweet on her.
She laughs it off - the lad is 20 years her junior. But soon the soldier is dragging the woman into an empty room and into disrepute. With-out waiting for consent, he whips out a razor and shaves off her pubic hair. Then he announces, as calmly as if he were proposing a flask of warm sake, that the cuckold must die. "Is there no other way?" the woman bleats. It appears not. Life moves fast in 1890s Japan.
As in the cinema of Oshima. "What a tremendous eye he has," remarked Bowie shortly after finishing Merry Christmas, Mr Lawrence. "He's so quick with his decisions . . . After the first couple of days, we realised it was going to be one-take stuff - one take, two takes. And that really fired us up; I think that got us through the movie more than anything else, this terrific momentum. You'd go through a scene, you'd be done, and then you'd be moving on to the next scene immediately, so you were always your character, with no chance to see the overall thing."
That immediacy survives intact on screen. Newcomers to Oshima - of whom there are many, as the films in the current two-month season at the BFI Southbank in London have long been out of circulation - will be struck by the briskness of his storytelling. Oshima has roamed hungrily across theme and style. His 1959 debut, A Town of Love and Hope, and the aggressively pessimistic Cruel Story of Youth and The Sun's Burial (both 1960)stake out previously uncharted territory where Nicholas Ray meets Italian neorealism in the Venn diagram of film history. They aren't an obvious fit, in auteurist terms, with In the Realm of the Senses or Empire of Passion. Perhaps this is what has made Oshima such a pressing contender for the title of Best Director Whose Films You've Never Seen. One certainly could not have foreseen his latter-day obscurity in 1969, when his masterpiece Boy was released, or in the late 1970s, when he was enjoying the sort of international infamy that can come only from a succès de scandale on the scale of In the Realm of the Senses.
And yet when his most recent picture, Gohatto, a portrait of the unrest caused in samurai ranks by a handsome new recruit, was released here in 2001, one broadsheet critic complained that it wasn't a patch on Ang Lee's Crouching Tiger, Hidden Dragon, which gives you some idea of what Oshima is up against these days. But it is precisely the deceptive nature of the films, their accessibility yet resistance to easy diagnosis, that makes them so distinctive. As Redford intimated, the full significance of Oshima's speculations may not become apparent until the final scene of any of his films. The pull towards those pay-offs, however, is mighty enough to turn the tide.
Watch the opening half-hour of Gohatto (the only film Oshima has made since suffering the first of three strokes in 1996) and you would be forgiven for thinking it was shaping up to be a gay Black Narcissus - which would be arresting enough, but it's not that simple. The experimental Violence at Noon (1966), like any serial-killer film, begins with a brutal attack, but then reveals its main concern to be the dissolution of a co-operative farming collective. (The collapse of leftist ideals is a pet subject of the director, who, as the critic Tony Rayns has noted, "suffered a series of tactical defeats" during his days of political activism at Kyoto University.) And Pleasures of the Flesh (1965) starts out like a jamboree-bag ofHitchcockian motifs (a virgin deflowered, a murder on a train, a suitcase of stolen cash), but then evolves into a languid erotic fable where
sex and money become interchangeable - which, I appreciate, sounds like great fun down at the building society.
Criminality provides one of the links between Oshima's films, from the thug who uses his girlfriend as bait to squeeze cash from lonelybusinessmen in Cruel Story of Youth, to the vulture-like parents in Boy, who use their blank-faced child as a similar instrument of extortion, to the violent lovers of In the Realm of the Senses and Empire of Passion. The director's capacity for bluntness brings him close in spirit to the rawness of early Fassbinder. There are undoubtedly shots in the part-glossy, part-tawdry Cruel Story of Youth for which that German maverick would have given his leather strides - a close-up of the urchin hero's face, cigarette and jawline sharply in focus as the rest of him dissolves into a warm blur; or the camera hovering impassively above him as he torments his girlfriend, whom he has just hurled into a river. Fassbinder would have got a naughty kick out of that, but Oshima is more compassionate. He does not idolise the ruffians who twirl a girl on the dancefloor until she's dizzy in Cruel Story of Youth, or the petty hoods in The Sun's Burial who hawk blood and stolen passports across desolate Kamagasaki slums.
In these early films, the camera sometimes feels embedded, to use a modern term associated with war, but Oshima is not impartial - he has a keen eye for injustice and for social power struggles in microcosm. He became fond of remarking in interviews that his interest in women, cinematically speaking, came relatively late, with In the Realm of the Senses and Empire of Passion. "In both [those films], I sought to represent revolution through the depiction of women and of the underlying currents in society," he said in 1981. "Not revolution through ideology alone."
But as early as Violence in Noon in 1966, he was tipping the balance towards a female interpretation of what might easily have been a male-dominated narrative. The film still looks bold today, in the way it sidelines the "Phantom Killer" with a skewed structure in which the dramatic power rests entirely in the hands of the women who know his identity.
All of which risks making Oshima sound forbiddingly earnest. In fact, he has a wicked sense of humour, as you would expect from someone who cites Luis Buñuel as the director he most admires (and who worked with that director's collaborator Jean-Claude Carrière on the Buñuelian Max mon amour). Desire in Oshima's work can be liberating, destructive and all-consuming, but that doesn't mean it can't also be ridiculous. When the killers in Empire of Passion get around to contemplating their crime, they ponder how they might be punished if caught.
“I once saw a man caned," whimpers Seki. "You're stripped naked, bound hand and foot, and beaten with one hundred strokes. It's horrible torture, your back laid raw, your flesh torn apart. No one can bear the agony." She is in tears by now, but her lover Toyoji leans in for minor clarification. "Completely naked?" he pants.
The Oshima season at the BFI Southbank, London SE1, continues until 14 October. For more details visit: www.bfi.org.uk 
Ryan Gilbey is the New Statesman's film critic