Like many other young Japanese, Rin, 21, punches her mobile phone keys very quickly. Holding her phone with two hands, and moving her thumbs deftly and smoothly, she quickly generates sentences on the small screen.

But unlike others, her main reason for typing on her keitai (mobile phone) is not to send e-mails, text messages or check the Internet. Instead, she writes bestselling novels. Rin is one of the most popular authors in the fast-expanding genre of keitai shosetsu (mobile-phone novels).

"I started writing stories on my keitai when I was a high-school student," Rin said. "Usually, you don't write novels during recesses between classes, and others might think you were a bit strange if you did that. But if you write on your keitai, nobody knows you are actually writing stories. I was writing stories when others thought I was sending e-mails."