It's an early weekday morning in Tokyo and the Japanese pub is already filled with a boisterous clientele, mostly pensioners. Sitting among them is Kengo Kuzuhara, taking notes.

The 41-year-old wants to know how his elders spend their cash, as he runs a stock fund that invests in things they buy. The strategy is paying off as Japan's baby-boomer generation reaches retirement age: Sumitomo Mitsui Asset Management Co.'s Active Senior Life Open Fund is gaining even as the market falls, and has beaten more than 90 percent of peers over the past five years.

Japan has about 34 million pensioners — more than the combined populations of Australia, New Zealand and Ireland — and people in their 60s or older control about two-thirds of household wealth. Kuzuhara is betting they will spend it on everything from healthy chocolates to property developers that can minimize inheritance tax.