But mixi quickly grew in popularity, and was heavily featured in the media as it sped toward a public stock offering in 2006. New members can join only with invitations from existing users, but some people began to send out invites randomly. The circle-of-friends concept was broken, and existing users began to lock their profiles and withdraw behind anonymous user names.

Naoko Ito is a typical denizen of Japan's online scene.

The office worker's video clips of her cats running amok at her house are among the most popular on YouTube Japan. Her blog features daily pictures of the feline antics and is popular enough to have spawned a book deal. But she doesn't post her name and in five years of uploading images has only rarely shown her face.

She says Japanese are just not used to putting themselves in the spotlight, and in the rare cases she has uploaded her picture it has been to show she is like everyone else.

"I want people to feel that I'm a very normal person, nothing special, just someone who likes cats," she wrote in an e-mail.

The reluctance to reveal oneself online is coupled with a general distrust of those who do, and foreign sites like Match.com have had to adjust. The site has had a local office since 2004, and has added Japan-only features like identity certification to generate an atmosphere of trust.

"When we did research on Japanese consumers, we found that the No. 1 reason for not using online dating is that they don't know if people are real or not," says Match.com's Japan president, Katsu Kuwano.

Match has increased its paying users in Japan by tailoring its approach to better fit marriage-minded Japanese women, timing advertising campaigns with national holidays when they travel home and face pressure from parents to find a mate.

But Kuwano says even among the women hunting for a spouse on the site, only 40 percent are willing to post a picture of themselves, and men are far less likely to respond without getting a glimpse first.

The company hopes to make more people show themselves online by defining itself in a less Web-centric way, latching on to the broader "konkatsu" movement in Japan, in which people actively seek out marriage partners. Match has also held offline events at Tokyo restaurants.

Even if the Japanese Internet isn't a place to meet new people, the fixation with anonymity still has led to an explosion in self-expression -- a sea change in a culture where strong opinions are usually kept to oneself. Anonymous Japanese bulletin boards like the massive 2channel are highly popular, with active forums popping up to discuss news events just minutes after they occur.

As is true elsewhere in the world, Japan's online anonymity can bring out the uglier side of human nature, but observers like the writer Shibui find that it is also freeing people to speak their minds.

"In using the Internet to anonymously talk about their troubles, or show off their strong points, or make people laugh," he said, "people in Japan can now interact based on what is actually being said, without worrying about who is talking."

Copyright 2008 The Associated Press.