Tucked away in his office in Japan's most prestigious university, Hideki Koizumi is worried. The towering cranes dotting the Tokyo skyline outside his building suggest a booming city, but the decaying suburbs tell a different story.
Dozens of condo buildings and hotels, and at least 45 skyscrapers are planned in central Tokyo in the coming three years, but the long-term view for the country's housing market is depressingly flat.
Japan's population is the world's oldest, with a third of its people aged 60 years or more, according to the United Nations. And with little immigration, it is shrinking. The nation lost almost one million people from 2010 to 2015.
There are already roughly eight million vacant homes across the country. The aging population will worsen this problem in the years to come, says Koizumi, a professor of collaborative community design, planning and management at the University of Tokyo.
Young people these days want to live in the centre of Tokyo and are fleeing the suburbs. Left behind are the elderly, who often struggle to maintain their homes.
"And their physical situation will become worse. So if no one will live with them in the suburban areas, who will look after them?" said Koizumi. Once the 2020 building boom triggered by the Tokyo Olympics is over, he warns, the problem will accelerate.
Noboru Takimoto sees things a bit differently. He is Tokyo's senior manager of overseas residential sales at Jones Lang LaSalle K.K., an international real estate company.
He acknowledges there's a vacancy issue but says it generally lies in the outer suburban and regional areas.
"I am not worrying about the vacancy increase so far," said Takimoto.
He says while prices for condos in the centre of Tokyo are now out of reach for many ordinary families, many more affordable ones are being sold in the city's suburbs.
Suburban homes cheaper than city condos
The condo price difference is indeed huge.
Central Tokyo apartments can sell for as much as roughly $120,000 per 3.3-square-metre block. In the suburbs, Takimoto says they're selling for about a third of that.
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The Japanese government has taken note of the growing problem of abandoned homes across the country. Last year, it announced a 10-year housing plan aimed at keeping the numbers of empty homes under control. Some will be demolished, others re-sold, and some made available for low-income families.
Municipal governments are joining the battle; some have started offering money to refurbish and remodel old homes to entice people to buy them.
For Tokyo, Hideki Koizumi, says more needs to be done.
"There is no growth management system in the Tokyo region. So we cannot control [things such as] where should a new housing project be located."
He says he's working with others to revitalize the problem areas and figure how to help the elderly. He says the first step is to introduce better programs to care for them; the second is to encourage young people to return to the suburbs.