Japanese society has long had a reputation for close-knit families and companies and for group culture. This year, however, the average number of people in a Tokyo home dropped below two for the first time.
NLI Research Institute says that, by 2020, living alone will be the norm in Japan. The think-tank's Akio Doteuchi says: "People are becoming more isolated. They used to live in friendly communities where neighbours would help them.
"Now people want to protect their privacy, so people in these communities have never even met their neighbours. They don't know if they live alone or it's a couple or a family.
"So sometimes people die alone without anyone noticing."
Mike Firn reports from Tokyo.