"Nobody Knows" is Koreeda's latest and probably best film, and one of the few to have won itself a tour of the global art house cinema circuit. The film arrives on the back of an impressive critical reception in its native Japan, as well as a Cannes win for Best Actor and Golden Palm nomination. Despite this relatively high profile, the film is still very much in the vein of the director's previous works, and as such is unlikely to appeal to viewers who have difficultly committing themselves to an unstructured film which is long and lacking in any form of traditional excitement. However, for Koreeda fans, "Nobody Knows" is an excellent film; brave, fascinating, heartbreaking, and sad, the film sees the director streamlining and refining his approach to produce what may well prove to be his masterwork.

"Nobody Knows" has a premise, rather than a plot, a fact which is likely to start alarm bells ringing in the mind of the average cinemagoer. Based on a real case (though a message at the start of the film points out that the precise details are fictional), the film starts as a young mother and her son move into a tiny apartment in Tokyo, carrying with them several large cases. Once the doors are safely closed, they open the cases, and out pop the rest of the children. Unfortunately, the mother (played by oddly named actress You, who was featured in the wacky "Matthew's Best Hit TV" program seen in "Lost in Translation") soon takes flight, sending the children only occasional funds, but otherwise abandoning them to survive as best they can.

The responsibility for keeping the family together, and indeed alive, falls upon the eldest, 12-year old Akira (Yuya Yagira), who struggles to put food on the table and hide his siblings from the eyes of the landlord. As time passes, the children gradually revert to an almost feral state, and it becomes painfully obvious that tragedy cannot be far away.

The film generally moves along in an almost dreamlike fashion, with only a handful of events driving the narrative. Through this, Koreeda allows the viewer to experience life in a manner similar to the children, as essential daily tasks vie for attention with video games and junk food. The film is shot on digital hand held camera, and without any kind of visual trickery or style. This approach, whilst often dragging the pace of the film to a crawl, is very realistic, and gives the proceedings the feel of a documentary. It is most effective when outside events suddenly intrude or are casually mentioned, such as final demand electrical and water bills. Since the younger children are blissfully unaware of what these things mean, and Akira has no real way of handling them, there is a growing tension, which makes the film a harrowing and often depressing experience.

Koreeda never milks the situation for cheap sentiment, even treating the mother's departure in a merely cursory manner. This works very well, and actually makes the film sadder, as the viewer comes to care for the children in a gentle, unforced way. Although there are a few moments of laughter and amusing scenes of childish inventiveness, the film generally heads in a downward spiral, slowly yet inexorably moving towards an emotionally wrenching conclusion.

The most impressive aspect of "Nobody Knows" is undoubtedly the acting. Apart from You as the mother, Koreeda chose a group of first time actors to play the children, and all are disarmingly convincing. There is quite obviously a great deal of improvisation on display, which adds to the film's realism and sense that we are being given a genuine insight into these children's struggles. Yuya Yagira well deserved his Cannes award (over such competition as the star of "Oldboy"), with a truly astonishing performance that shows emotional range, perfectly capturing the torment of a boy forced to take on such a crushing and impossible responsibility.

Although there is obviously much to admire about "Nobody Knows", it is fair to say that the film has its faults, primarily the slow pace. Coming in at nearly two and a half hours, the film is overlong, and certainly drags during the middle. Koreeda has an incredible eye for detail, though the downside to this is that he spends a great deal of time cataloguing mundane events, and whilst this certainly makes the film realistic, it at times also makes it boring. Whilst the filmmaking technique no doubt reflects the children's situation and feelings quite accurately, it is questionable whether viewers would wish to subject themselves to a similar ordeal.

The minimalist approach may also deter some viewers, as the film mostly takes place in one room, and has little in the way of visual trappings. Although Koreeda does make full use out of the sparse locations, and plays the inherent claustrophobic nature of this to full effect, again this at times does make parts of the film seem somewhat superfluous and in need of tighter editing.

At the end of the day, these factors neatly sum up "Nobody Knows", as some viewers will find them fascinating and brave moves, whilst others will simply scratch their heads and yawn with boredom. However, for those with patience, the film comes with a high recommendation as a grueling yet fascinating and painfully realistic experience. Whether or not its success will serve to take the director's works to a wider audience remains to be seen, but for his fans the film is likely to be seen as a landmark.