Mori Tower in Roppongi Hills in Tokyo

Japan's economy is barely growing, its population is falling and wages have long been stagnant, but investors both inside and outside the country see surprisingly big opportunities in its property market.

"It has become difficult for general households to keep up with rising housing prices while employment and income are stagnating," Deutsche Bank said in a June note, citing data showing Tokyo condos cost more than nine times annual household income.