NEW YORK (TheStreet) -- Shares of Mizuho Financial Group (MFG) were gaining 3.6% to $4.38 on heavy trading volume Tuesday after the Japanese bank reaffirmed its plan to cut the number of shares it owns in other companies.

Mizuho Financial reaffirmed its commitment as a response to new Japanese governance rules, according to Bloomberg. The new rules require Japanese companies to justify why they hold shares in other companies to ensure they use their capital affectively.

"It's important to realize gains on shareholdings," CFO Junichi Shinbo said at the bank's annual meeting on Tuesday. "We will start the unwinding process soon and sell shares that need to be sold."

The bank promised to gets rid of cross-shareholdings that aren't "meaningful" on June 1.

About 3.7 million shares of Mizuho Financial were traded by 9:40 a.m., above the company's average trading volume of about 346,000 shares a day.

MFG ChartMFG data by YCharts