Further consolidation among Japan's regional banks is inevitable given the rapidly aging population and ultralow interest rates, according to an adviser to the Financial Services Agency.

The Bank of Japan's radical stimulus program, which has pushed interest rates to near or below zero, is severely cutting into bank profits and could destabilize the sector in the not so distant future, said FSA adviser Naoki Ohgo.

"There are only a handful of regional banks successfully making money in niche areas," while many others are struggling to find new business models, Ohgo said in an interview Friday.