A growing number of retirees in Japan are falling victim to fraud, underscoring one of the downsides of promoting personal investment in the world's most aged nation.

Combating the problem is a rising challenge for the government of Prime Minister Shinzo Abe, as it encourages Japanese households to shift more of their ¥1.654 quadrillion ($14 trillion) in assets out of savings accounts and into investments that boost the economy.

The rally in Japanese stocks that's bolstered wealth for shareholders has also rekindled interest in riskier investments among some retirees — many of whom retreated from the market more than two decades ago when the country's asset bubble imploded. Surging equities contrast with annual returns of about 0.02 percent on savings accounts at Japan's biggest banks.