Once a month in Yokohama, a city just outside Tokyo, parents gather in a community hall to discuss children who won’t leave home.
Some of the children are grown-up but have lived in their rooms for years refusing to emerge except at night when they rummage the house for food. In most cases they are linked to the outside world, if at all, through the electronic umbilical cord of an internet connection.
Acute social withdrawal first triggered widespread media interest in Japan in the early 1990s.
Known as hikikomori, teenage shut-ins began their journey to isolation by refusing to attend school. Today, many of those former teenagers are grown men and women.
Government estimates say there are 700,000 of them – mostly males – though many specialists believe the real number is far higher.
Most hermits spend their days locked away, watching TV, surfing the web or playing interactive games.
For years,the problem was dismissed as teenage angst or laziness rather than a genuine mental disorder, says Dr Tamaki Saito, one of Japan's leading hikikomori specialists. The media made fun of sufferers. Treatment was rare and difficult to get.
Frustrated parents would try persuasion, cajolery and sometimes even violence before giving up. “In some cases they’re afraid of their children, or afraid what might happen to them if they kick them out to fend for themselves,” says Saito.
Though hikikomori wrestle with age-old problems of depression and self-esteem, their condition is quintessentially modern.
Their alienation is often triggered by rebellion against the education conveyor belt and social pressure to succeed. Many come from middle-class families with financial and technological resources, says Dr Yuko Kawanishi, author of Mental Health Challenges Facing Contemporary Japanese Society. "The minimum condition to become a hikikomori is to have your own room," she says.
The cyber-evolution is not to blame for the phenomenon, but it has facilitated it, say psychologists like Kawanishi.
So in a country where so many have swopped real life for a computer-mediated fantasy world some parents in the Yokohama support group worry that new immersive technologies could incubate a new generation of shut-ins. Head-mounted virtual reality displays such as Rift, are just around the corner.
“My son already has access to the internet and I sometimes feel that it makes his condition worse,” said one mother, who identified herself only as “Kyoko”.
“He has a community of people online who he never physically meets but who sustain him, and that means he never has to go out. More technology might isolate him further.”
The only thing that might hinder the 21-year-old, she said, is finding the money to buy equipment.
Virtual technology pushes us closer to the dystopian world depicted in Neuromancer, the cult 1984 novel by William Gibson, says Tim Hornyak, a veteran Tokyo-based technology writer.
The novel, partly set in Japan, is credited with introducing the idea of cyberspace and featured characters who “jack in” via neural interfaces to interact directly with the virtual world.
As computer devices become smaller and cheaper, they’re getting closer to our body, says Hornyak – “and the brain is the final frontier”. He notes that scientists are developing so-called brain machine interfaces, devices that experiment with moving objects using brainpower alone. “The possibility exists for these more immersive devices to suck people in more than they already are,” he says.
Much of the literature on online addiction concerns virtual role-playing games such as Second Life, which are known to cause excessive devotion.
The games have been blamed for a host of social problems and even for causing deaths. In one of the most notorious cases, a South Korean couple starved their infant to death in 2010 while they obsessively “raised” a virtual young girl in an online computer game.
The irony, says Horynak, is that such people are part of a community. “They’re interacting with people around the world, but not with people around them.
“The more people have these devices the less they seem to be interested in interacting with the rest of the world.”
He is struck by the sight of commuters on Tokyo trains using smartphone devices which demand attention in a “more aggressive and comprehensive way” than books or newspapers.
“It’s a trend toward isolation. The more these devices becoming ubiquitous – I think we’ll see more people become recluses,” he says.
Once considered particularly Japanese, social withdrawal is beginning to affect developed societies elsewhere.
High unemployment and shrinking opportunities for the young in much of western Europe are forcing more to live at home.
A recent survey in a report by the Prince’s Trust found that four out of 10 unemployed young people in the UK said “anxiety had stopped them from leaving the house”. Half said they “avoided meeting new people.”
The remedy to this alienation increasingly comes from hikikomori themselves. Kazuya Ishida, who is 37, spent a decade shut in before emerging back into society four years ago.
He now runs a group of former sufferers who meet in the real world once a week to talk and support each other.
Ironically, he found the strength to leave his room from online friends.
“I don’t blame technology,” he says. “If it wasn’t for the internet, I might never have left.”
For more on the Prince’s Trust report see http://www.princes-trust.org.uk/ macquarieyouthindex/index.html