EVERY MORNING, suburban trains in western Tokyo ferry the dark-blue army that keeps this Asian superpower humming. As the carriages fill, silence descends, punctuated only by the rustle of newspapers and the odd winter cough. In the few spare seats, salarymen and office ladies doze as the announcer, voice tuned down to the morning hush, reels off the stations. The reverie is broken by a young man who sits legs spread wide, eyes glued to his mobile phone, the hiss and pop of his iPod leaking rap music from his earphones; oblivious to the irritated sideward glances of his fellow passengers. Dressed in the international hip-hop uniform of baggy clothes, white sneakers and back-to-front baseball cap, he looks as out of place as jeans at a wedding. The surly Japanese rap fan is growing increasingly common here as hip-hop culture goes from underground to mainstream. The mix of dance beats, rapping and attitude has slowly seeped into Japanese culture and the country's biggest acts - Dragon Ash, Zeebra, K Dub Shine, Mabo and Rip Slyme - now sell millions of discs between them. The second best-selling artist for 2005 in the Japanese pop charts was a rap/hip-hop act, Ketsumeishi, according to Orico Japan, and Japanese hip-hop has sprung up its own group of fashionistas, such as Jun Takashi and Nigo, who have become stars in their own right (Nigo's label A Bathing Ape supplies clothing and accessories to the Beastie Boys and Beyonce). Japanese hip-hop recently won the ultimate badge of mainstream credibility when the country's biggest car manufacturer, Toyota, used a Rip Slyme song in its commercial. 'Hip-hop is huge here right now,' says Jennifer Hodgins, international director of licensing company JMS Corporation, which represents Street Wars, a hip-hop-inspired fashion label. 'One sign of how big it is is how teen idols have started to incorporate it into their music. Even the princess of J-pop Namie Amuro.' Japan has a long tradition of aping musical styles pioneered in the west, particularly the US, but many are surprised by how enthusiastically the country's fickle young people have embraced a culture radically different to their own. 'You have probably the most fluent, eclectic youth culture in the world here, and it takes to its heart the music of poor people from the Bronx,' says Kyle Cleveland, who teaches sociology at Temple University, Tokyo. 'There is a huge cultural gap there, bridged by aggression, sexuality and confidence.' Even those who make a living from rapping have been taken aback. 'I'm surprised by how far hip-hop has come in Japan,' says bilingual, US-based Japanese star Shingo2, who is recording his fourth album with superstar DJ Krush. 'But we've been doing this throughout history and making something our own is one of our strengths. And rapping suits Japanese because it is based on syllables and you can break up the word in the middle and make it sound on-beat; stuff that would sound awkward in English.' The movement has come in waves to Japan. The earliest key event was marked by the 1982 release of classic hip-hop movie Wild Style and the arrival of New York-based Run-DMC the following year with It's Like That. Initially there was far less interest in the English lyrics or music than there was in the breakdancing. Local acts began to spring up, however, such as B-Fresh (which later included DJ Krush) which was the first hip-hop group to get signed in the late 1980s. But the first million-selling hip-hop hit didn't come until 1994 with the crossover hit Boogie Back Tonight by rap act Scha Dara Parr and pop artist Kenji Ozawa. During the rest of the 90s, the R&B boom helped spread the hip-hop style, driven by artists such as Misha and Hikaru Utada. Theories abound why otherwise reserved youngsters from Tokyo to Okinawa find the crotch-grabbing antics of US rapping so appealing, but most say that like rock'n'roll and punk, hip-hop feels exotic and liberating in this famously buttoned-down culture. 'Hip-hop allows for the expression of unabashed individual desires and needs, and in a repressed country that is very attractive,' says Dan Grunebaum, music critic with magazine Tokyo Metropolis. Cleveland agrees: 'It's a surrogate identity that allows Japanese to articulate things they could not otherwise. The themes are confidence, aggression and these are things that are not cultivated [in Japan].' While for many this means simply the freedom to sing the praises of cars, sex and well-upholstered women like 95 per cent of other pop music, it is also one of the things that makes hip-hop so politically interesting for those who study Japan, especially on its fringes where anti-American themes can be common. Kakumakushaka, a native of Okinawa incensed at the presence of US bases in the prefecture, for example, raps about a military helicopter crash in 2004 that sparked some of the biggest protests there in years. The angry polemic rails against the accidents, violence 'and murder machines in the sky' that have plagued Okinawa thanks to the presence of over 20,000 Marines, before concluding that the natives would rise and 'fight for peace'. In the video for 9.11, the Japanese group King Giddra rap over a shot of a mushroom cloud: 'Rest in peace to NY, City of Dreams/ Pay back, even more will die/ If someone can explain, do it/ Is this terrorists against a nation? No, that's mistaking one part for the whole/ The media's strategy: push good and evil/ And I see an atom bomb that fell in the past/ I dreamed of a new century/ But everyone dies if this stupidity goes on.' Such protest themes - rare in the pop pap churned out by the country's music giants - were common in the 60s and 70s folk and rock boom in Japan, but have largely been absent since from popular music and reflect rising resentment at what some see as Tokyo's subservience to US foreign policy. Every era finds its musical form and rap's street poetry, with its anti-establishment roots and aspirations to universal brotherhood, seems to have a lock on Japan. 'If you're going to find political music, you're probably more likely to find it in hip-hop than rock or pop,' says Ian Condry, a Massachusetts Institute of Technology professor and author of the forthcoming book, Hip-Hop Japan. 'It's a home for people that are not pretty or rich, but who have something to say.' In a country that has shifted dramatically rightwards under Prime Minister Junichiro Koizumi, it is not difficult to see how some of the anti-US sentiment in rap might shade into nationalism. Zeebra were inspired by the Kitano Takeshi movie Brother, which showed the Japanese star blowing away an American gangster who called him 'Jap', to write their hit Neva Enuf, which in Condry's words: 'Takes the voice of the exiled Yakuza who kicks butt in the US.' (One of the odder cultural phenomena in Tokyo is right-wing bosozoku biker gangs adopting hip-hop's style and attitude). But although Shingo2 says he sometimes sings about 'national pride' and Japanese history, he believes hip-hop themes are inimical to a narrow nationalist worldview. 'If you're really down with hip-hop you should be talking about unity,' he says. Others say such lofty political themes are beyond the concerns of most rappers in Japan, who are mostly the children of comfortable, conservative salarymen. 'Most Japanese young people are not interested in serious history or political messages,' says rapper Konie. 'We have no history of discrimination in Japan, so we can't be real hip-hop: music is based in people's lives. To be real, we have to rap about our lives. There is no point in me being a gangster or rapping about discrimination. That would be fake.' Perhaps, or maybe Japanese rappers have fallen for the myth that they live in a conflict-free country, news to the hundreds of thousands of Korean and Chinese-Japanese who live there. One of the few to raise their heads above the parapet is KP, a group of zainichi (resident in Japan) Koreans who rap about North/South Korea relations. The top of the charts are unlikely to be bothered, though, by that sort of fare. Like any pop music, hip-hop is increasingly homogenised by the music industry until is it easily digestible, with lyrics that wouldn't tax a 12-year-old. And while Japanese rap is mercifully shorter on 'bling', 'bitches' and 'hos' than its US counterpart, it can match it for rubbish lyrics. In their song Hungry Strut, Kohei Japan boast about their music: 'Eat it once and the flavour won't stop/ Addictive like salty dried squid.'