In Deep Love, a wildly popular Japanese story of teenage heartbreak, Ayu prostitutes herself to raise money for her boyfriend Yoshiyuki's life-saving heart surgery. But instead of using her contribution to pay for the operation, his parents spend it and Ayu dies of Aids. Steamy melodramas with tear-drenched endings have long been a staple of Japanese and South Korean popular entertainment. But Deep Love, which recently appeared as a movie and a TV series, boasts an unusual feature: it began life on a mobile phone. Facing some of the longest railway commutes in the world, Tokyo residents used to find diversion in fat books and newspapers. Increasingly, however, commuters can be found squinting into the glowing screens of their mobile phones, or keitai. Literally meaning 'something you carry with you', the keitai has become Japan's most ubiquitous accessory. In February, the number of mobile phone subscribers in the country exceeded 100 million, which means that, apart from small children, octogenarians and Luddites, most of its 128 million people own at least one. Standard phone features include internet browsers and digital cameras. With bigger screens and faster downloads, haiku, manga and now graphic novels are viable. Shinchosha was among the first major publishers to spot the potential of electronic books. In 2002, it launched its Cell Phone Pocket Edition, offering unlimited access for 210 yen (HK$13) a month. The service was initially conceived as a sort of arty electronic literary magazine, but young popular writers began contributing short stories instead and the service gradually built up 30,000, mostly female subscribers. Four years ago, publisher Starts began selling Deep Love as a download, persuading thousands of young, mainly female readers to log on. Another Starts story, Koizora, was later released in hardback and sold 1.2 million copies. Japan's first million-selling mobile phone novel had arrived. Koizora is due for release as a movie later this year. Meanwhile, Starts is collecting entries for the first mobile phone novel prize in August. Larger, established book publishers with flat sales are quickly learning that if young readers aren't going to come to them, they'll have to take their product to the readers. Kadokawa Publishing, for example, recently released many of its older titles online and found that they were popular with women in their 20s and 30s on boring late-night train journeys. 'It's convenient when I need a change of mood after work. Bookstores are usually closed when I get home,' a 28-year-old told the Nikkei newspaper. The genre even has its own literary stars, such as Mika Naito ( http://micamica.net ), the so-called queen of the mobile phone novel. Serialised on Shinchosha's Pocket Edition, her novel Love Link was accessed 1.5 million times within five months. Naito wants to publish in English and has posted her work on YouTube (youtube.com/micanaitoh). Internet bloggers have also launched unlikely careers on the very small screen. Hen-pecked husband Kazuma, for example, considered the time-honoured solutions to domestic hell - more work, the golf course or the comfort of the local bar - but bashed out his frustrations on his home computer instead and put the results online. More than three million hits later, Kazuma's oni-yome nikki (demon wife diaries) is among the most famous in Japan's blogland, and the monster he spawned has been turned into a book, TV series, video game and now a movie. In a country with the largest number of bloggers per capita in the world, there are likely to be many more stories where Kazuma came from. Thousands of Japanese titles can now be accessed for about 210-450 yen a pop - cheaper than a paperback and without the added bulk in handbags and briefcases. The newer e-books, which can usually be accessed for two or three months before the subscription lapses, have developed their own literary tics, including serial cliffhanger endings and a small cast of characters - two to four people. 'I thought the idea of a keitai novel was a bit dumb because the screens are so small,' says 25-year-old Eriko Saito, a travel agency worker. 'But you quickly get into them because the stories are so compelling and easy to understand, and the endings keep you coming back for more. I'm totally addicted.' Foreign authors have since waded into the market. American writer Barry Yourgrau serialised his children's short stories over NTT's i-mode network and has just been signed up by Shinchosha, which began publishing his work in January. 'When I was over there I noticed that everyone was surfing the net on their cell phones,' he says. 'It's a super-evolved internet cell phone culture.' It's hard to estimate the value of this market, which didn't exist five years ago. The Nikkei recently claimed sales of e-books had topped nine billion yen in 2005, half of which was accounted for by mobile phones. That figure is likely to have doubled since then. The trend has its detractors. Some say the truncated, slang- rich content of keitai novels hardly qualifies as writing, let alone literature. Others query the health costs of hunching over and squinting into tiny flickering screens for hours. The popular press has coined the phrase oya yubi seddai - the thumb generation - to describe the many young keitai-users, fingers racing over tiny consoles. They may need to coin another: nekose seddai - the humpback generation. But in a country famous for incubating new technological trends, it's only a matter of time before smart engineers find a way out of these problems. Consumer electronics giant Matsushita recently developed a 5.6-inch, high-resolution colour screen called Words Gear reader, for reading e-books. The company has formed a joint venture with Kadokawa Publishing to release 400 titles. Sony has also just launched the 0.30kg Reader, a 6.9 x 4.9-inch machine that uses i-Tunes technology to purchase e-books from the company's own Connect service (ebooks.connect.com/). Both can accommodate full-length books on pin-sharp, non-flickering screens For many, the entry of two major manufacturers is a sign that the paperless book is about to enter the mainstream. 'Is the Sony Reader the library of the future?' asked the Weekly Standard last month. It's only early days, but the mobile phone could one day make the printed page as obsolete as the traditional kimono.