You didn't need prophetic powers, back in the 1980s when the personal computer was starting to show its potential, to foresee something like Internet addiction. It should have been obvious. It was, to science-fiction writer William Gibson. Reminiscing to Time magazine in 1995, he recalled his shock, as he walked by a video-game arcade sometime in the late '80s, at how absorbed the players were in their glowing screens. "I could see in the physical intensity of their postures how rapt the kids were," he said. "These kids clearly believed in the space the games projected. They develop a belief that there's some kind of actual space behind the screen."

Gibson gave that space the name we know it by today: cyberspace. If it were physical, we'd say it was getting pretty crowded. Japan's health ministry, in a report released earlier this month, estimates the number of "Internet-dependent" junior and senior high school students at 520,000 — 8 percent of the nationwide junior and senior high school population, versus 2 percent among adults.

What sets "dependency" apart from healthy use? Any dividing line is bound to be arbitrary, but the key warning signs are sleep loss and a difficulty connecting to anyone or anything except via computer. Call them addicts or Internet-dependent or simply citizens of somewhere other than "here"; anyway, 22 percent of senior high schoolers typically spend five hours or more of a day off school online. "Few consider themselves ill," a specialist in Internet dependency tells the Asahi Shimbun. Clearly he takes a different view.