Mizuho Financial Group Inc., the mega-bank that added dozens of stock analysts and salesmen in the past year, is seeking to loosen Nomura Holdings Inc.'s stranglehold on the nation's potentially lucrative yet elusive retail brokerage business.

Tokyo-based Mizuho wants to overtake Nomura as the nation's biggest equity firm by client assets and revenue, according to Yohei Osade, global head of Asian equities. To achieve the goal, the bank's Mizuho Securities Co. unit will make the most of its expanded research capability to step up marketing to non-institutional investors, as well as boost execution services, Osade said in an interview in Tokyo.

The ambitions reflect Chief Executive Officer Yasuhiro Sato's efforts to diversify from Mizuho's traditional strengths in loans and bonds to generate more fee income as negative interest rates squeeze lending profitability. Nomura, Japan's biggest securities firm, has relied on profit from its retail brokerage network for years, dominating a market that global banks including Merrill Lynch and Morgan Stanley have failed to penetrate as risk-averse households hoard cash.