Remember that old philosophical brain-teaser that states that if you have a boat, and over a period of time you replace each piece of wood bit by bit as it begins to rot, is it the same boat as when you started once you have replaced every last plank? A similar conundrum can be readily applied to the question of national identity.

Perhaps more than most countries, on a purely superficial level modern Japan bares little resemblance to the country it was a hundred years ago. Within the cultural, political, economic domains, Japan has certainly absorbed more from abroad than it has given in return. The only level in which pure "Japanese-ness" remains unsullied is ethnically. You may speak Japanese, you may look Japanese, you may have been born in Japan, but unless you can trace your lineage back to the Tokugawa period, to the indigenous inhabitants you'll always be an outsider.

Hair trendily frizzed, and a defiant swagger in his walk, Sugihama could be any other rebel-without-a-clue Japanese high school student, were it not for the fact that he's not just the kid from the wrong side of the tracks; he's from the wrong side of the Japan Sea, a second-generation North Korean, or zainichi. However, such definitions sit badly with him. "If I'm a Japanese resident Korean, that means I'm going back". Fat chance, having already been thrown out of the austere cloistered corridors of his North Korean School for cursing at the teacher in Japanese. His decision to move to a Japanese school wins him a certain degree of respect from his former fellow zainichi students, but it opens him up to a stream of violence from his new classmates.

Fortunately his greatest form of defence comes from the boxing lessons he has received from his father (Yamazaki) since childhood. His second in that like most Koreans, to the outside eye he is indistinguishable to the Japanese, a factor that seems the most likely passport into full integration with his adapted homeland when he meets pristine high school princess Sakurai (Shibasaki, then hot off her memorable role as the minx with the scythe in Battle Royale). However, for all their shared love of non-Japanese rap music and Bruce Lee films, the question still lingers as to whether Sakurai is prepared to accept Sugihama at face value once she learns his about his true origins.

Foreign critics have been quick to point out Japan's strained relationship with its neighbouring Asian countries, and the prejudice faced by ethnic Asians living in Japan. Some have stated that the issue is completely brushed under the carpet, but the truth is, Go, which received a simultaneous theatrical release in Japan and South Korea, is not the first film treatment of the subject. Nor is it the first film about discrimination directly against Koreans. It is however the first major film to challenge existing preconceptions about Japanese identity within such a commercial format. That it does so in such a moving and high-spirited fashion makes it even more worthy of note.

But it's not just the issue of prejudice, reflected in the unconscious racism of Sakurai, which is tackled, but that of racial identity in general. In the early scenes Sugihama's father cashes in his North Korean passport for a South Korean one, ostensibly so that he can take his wife (Otake) on holiday to Hawaii, much to the disgust of his son. One of Sugihama's former classmates from his North Korean junior high school berates him for wearing jeans and listening to Mariah Carey (admittedly, a heinous crime whatever part of the globe you stem from). Sugihama's desire to break through the boundaries is shared by his best friend, nerdy brainbox Jong-Il (Hosoyamada), who sees the insularity imposed upon them through the exclusively Korean speaking "minzoku" schools in which they are drilled with the communist spirit as equally unhealthy. He is instrumental in pointing to a broader world outside of both Japan and Korea when he lends Sugiyama a translated copy of Shakespeare's Romeo and Juliet (from which the film's opening quote, "What's in a name? That which we call a rose, by any other name would smell so sweet?" is taken) it's a reminder that, as our hero constantly tells us, this is after all a love story.

Adapted from the novel of the same name by Kazuki Kaneshiro, himself a zainichi, from the opening scenes where our beleaguered protagonist receives a pasting on the basketball court (from his own team nonetheless), Go sets forth its agenda in a vital, spirited fashion, deeply reminiscent of Danny Boyle's Trainspotting in its raw energy. However, along with its semi-comedic asides, surrealistic touches, and a style marked out by a use of such modernist techniques as freeze frames and jump cuts laid down to a compulsive pounding soundtrack and a continuous voiceover from its sage-like protagonist, its focus on Asian ethnics living in Japan is likely to draw attention away from director Yukisada's previous work - Sunflower (2000), Luxurious Bone (2001), and his contribution to the six DV-shot Love Cinema series Enclosed Pain (2001) - to his role as AD on Shunji Iwai's Swallowtail Butterfly (1996), another tale of Asians living in Japan, which treated its subject matter in a similarly glitzy fashion.

Through the in-your-face violence and dazzling virtuosity of its approach, Go often comes dangerously close to over-stating its case in a manner that is more cinematic flourish than verisimilitude. In this respect it's easy to criticise Go's focus on the individual racism that its protagonist suffers from over the deeply ingrained institutionalised racism which ensures that even after several generations, many resident Koreans are still refused Japanese passports.

Nevertheless, Kubozuka, the top teen heart-throb of Japanese cinema in 2002 through his roles in Laundry and Ping Pong, fills his role as Sugihama with an affable punkish charm that is hard to resist. Go's dramatic trajectory may be a fairly well travelled one, but in its stronger moments, such as the romantic interplay between Kubozuka and Shibasaki, it's undeniably affecting, and as such, one of the most outstandingly compelling and thought-provoking films of its year.