Where there's a will, there's a way. That's what banks across Japan are counting on as they try to keep hold of the ¥50 trillion in wealth left by their customers each year when they die.

With more than a million Japanese dying annually, smaller banks are losing not only customers but also their savings, as heirs migrate to large cities where the biggest lenders hold sway. Regional banks lose about 60 percent of funds that are subject to inheritance, Fidelity Investor Education Institute estimates.

Now, in a country where about a quarter of the population is over 65, local lenders including Mie Bank Ltd. are turning to trusts to secure the next generation of clients and their deposits.