Maggie Jones in the New York Times (via longform.org):

"One morning when he was 15, Takeshi shut the door to his bedroom, and for the next four years he did not come out. He didn’t go to school. He didn’t have a job. He didn’t have friends. Month after month, he spent 23 hours a day in a room no bigger than a king-size mattress, where he ate dumplings, rice and other leftovers that his mother had cooked, watched TV game shows and listened to Radiohead and Nirvana. “Anything,” he said, “that was dark and sounded desperate.”

[Takeshi] suffered from a problem known in Japan as hikikomori, which translates as “withdrawal” and refers to a person sequestered in his room for six months or longer with no social life beyond his home. (The word is a noun that describes both the problem and the person suffering from it and is also an adjective, like “alcoholic.”) Some hikikomori do occasionally emerge from their rooms for meals with their parents, late-night runs to convenience stores or, in Takeshi’s case, once-a-month trips to buy CD’s. And though female hikikomori exist and may be undercounted, experts estimate that about 80 percent of the hikikomori are male, some as young as 13 or 14 and some who live in their rooms for 15 years or more."