Japan has long grappled with what to do about hikikomori – the social hermits who seal themselves off from the world, sometimes for years, retreating from all human contact. In the past, these recluses were thought of as a youth problem: troubled teenagers, rudderless young men. But that framing no longer holds. Japan’s shut-ins are growing old, and the parents keeping them alive are growing older still. The average hikikomori is now 36.9 years old, according to the Asahi newspaper, citing a...