At first glance, the Japanese pop scene can be baffling. The music is super-sweet and hyperdynamic, an offshoot of Japan's kawaii culture of cuteness and a literal world away from earnest singers with guitars or scathing rappers with laid-back beats. While there are solo stars and boybands, just as in western pop, there's a particular cultural excitement around girl groups.
These can be relatively small troupes like Perfume or Momoiro Clover Z, or bands who have so many singers they run the risk of outnumbering their audiences, such as AKB48, who can boast 130 singers on their payroll and are not only Japan's biggest selling group, but the world's largest pop troupe.
As East Asian culture has traditionally valued teamwork and harmony above individualism (see How East and West think in profoundly different ways), so groups and collectives have tended to be more popular in Japan than solo artists. In the case of AKB48, competition to join the band is not only fierce, it's televised, in a tense spectacle that makes The X Factor look calm and sedate by comparison.
As part of the BBC's Japan Season, Storyville presents the documentary Tokyo Girls, a film by Kyoko Miyake, which explores the phenomenon of idol groups, who have come to dominate J-Pop, through the eyes of Rio, an aspiring performer, and her devoted fans, who call themselves Rio Brothers.
Rio's fans are, in the main, adult men, some in their mid-40s, and they call themselves otaku, a word used to describe someone with an obsession with an item of popular culture that is so great it can detract from their abilities to socially interact, ie. an equivalent to nerd or geek. Otaku display the same passion and devotion as any teenage Justin Bieber addict, and in some cases are prepared to give up their careers and devote all their savings to following their favourite performer.
This isn't an isolated situation. While J-Pop remains hugely popular in Japanese culture, idol fans are an entirely different social demographic than pop fans in Britain. More male than female, and older too. So while some Japanese music fans of a certain age might spend their time painstakingly recreating the music of Radiohead, others are bent over the craft table, making immaculate glittery gifts for their pop idols.
In the main, idol singers are presented as fantasy versions of perky schoolgirls, full of pep and vim, and entirely innocent about adult matters. Even Babymetal, a band who apply J-Pop sensibilities to heavy metal, sing far more about chocolate and dancing than they do about Satan or sex.
There are a lot of performers to choose from, as the film explains, there are over 10,000 teenage girls who perform as idols in Japan at present. They perform live webcam shows and in small venues similar to karaoke bars, called idol cafes. Tokyo's Akihabara district is the hub of idol activity, in a business that is said to be worth $1 billion a year.
According to cultural commentator Akio Nakamori, there's a distinct - and surprising - economic reason why these men devote their time and attention to idol performers, and it's to do with the Japanese recession: "There are parallels between 1970s London and Tokyo today. The economy stagnated and the cultural scene was dead. People were looking for something new. London invented the Sex Pistols. The Japanese answer was idol culture."
So it's both countercultural - fans speak of being united with their idols against the establishment - and typically capitalist, just like most western pop music. Notably, though, homegrown Japanese music never entered anything like a grunge phase (quite a stretch for a country that only relatively recently came to an understanding of depression). Rather than channelling painful emotions into genres like punk rock, idol culture instead offers escapism into an upbeat kawaii fantasy.
Interactions between performers and fans have an etiquette of their own, with tightly observed parameters and expectations. There are fans who think nothing of spending thousands a month on meet and greets, $10 a time for a CD and a chance to shake hands and have a photo with their chosen favourite. And part of the appeal is that these performers are accessible.
The idol phenomenon has had an unexpected side-effect, in that the female performers, who often have had to work to a punishing schedule, have attained a status that is relatively new in Japanese culture. Journalist Minora Kitahara explains: "In idol culture women are the stars. There may be nowhere else in Japanese society where we’re the driving force."
Although this breakthrough only exists within the tight parameters of the idol fantasy world. In 2013, a video appeared on AKB48's YouTube channel of a weeping Minami Minegishi (then 20) who had shaved her head in an act of public shame in order to apologise for spending the night with her boyfriend.
There's an inverse parallel with the stereotype of western boybands and the young girls who adore them. The suggestion is that boyband stars are a proxy for romance, for fans too young and nervous to experience the real thing. And if that broad-brush explanation contains a germ of truth, a similar thing applies in the case of, say, Rio Brothers, except these are men for whom genuine romance is either too daunting a prospect, too much of a compromise or simply an unattainable goal.
So it seems that idol performers remind the otaku of a time in their lives when fun and optimism were palpable things, and rather than face a dreary or potentially upsetting reality, they choose to escape into the fantastic realm of fandom, where they know exactly what to expect. As Mitacchi, a fan of P.IDL singer Yuka explains: "I stopped dating when I met Yuka... I'm rational enough to know that nothing will happen with her in reality."