Mitsubishi UFJ Financial Group and Sumitomo Mitsui Financial Group will start divesting ¥1.32 trillion ($8.5 billion) worth of strategic shareholdings in Toyota, people with knowledge of the matter said, the strongest sign yet that Japan’s big businesses are getting serious about unwinding their vast network of cross-held shares.

The banks will sell in stages and take advantage of Toyota’s plan to buy back its own shares, said the people, who asked not to be identified because the information isn’t public. The world’s No. 1 carmaker announced a ¥1 trillion buyback program on May 8, representing about 3% of its stock and significantly larger than its previous repurchases.

The unwinding is being crafted to minimize the impact on the company’s share price, the people said. Although the government has been pushing corporate Japan to unwind cross shareholdings, forged over decades to cement business relationships, the biggest banks and businesses had been slow to do so. Given its scale and significance, the Toyota deal could trigger a broader wave of looser equity ties in Japan.

Representatives for Mitsubishi and Sumitomo Mitsui declined to comment. Toyota representatives didn’t respond to a request for comment.

The Mitsubishi stake is worth roughly ¥700 billion, while Sumitomo Mitsui holds about ¥620 billion of Toyota stock, according to data compiled by Bloomberg. They will sell their Toyota shareholdings over an extended period of time lasting a few years, dramatically reducing their stakes or divesting them entirely, the people said.

Mizuho Financial Group, the other member of Japan’s trio of megabanks, doesn’t own a significant stake in Toyota.

The stake sale program follows a robust run-up in the price of Toyota’s shares, which are up about 26% this year on top of a 43% rally in 2023.

Some insurers have already indicated that they plan to reduce their cross-corporate shareholdings to zero. Authorities have been pushing them to accelerate the divestment of their holdings, which were seen as one of the factors why they colluded to fix prices in contracts with corporate clients.

MS&AD Insurance Group Holdings, Tokio Marine Holdings and Sompo Holdings are the top nonlife insurance companies holding stakes in Toyota. If they were to join the banks in divesting shares, the total would top ¥3 trillion.

Toyota is also unwinding cross-shareholdings within its network of manufacturing partners. In November, the carmaker announced plans to lower its stake in electric parts maker Denso to 20% from 24%. Prior to that, Toyota committed to selling some of its stake in telecommunications company KDDI for ¥250 billion. While the sales serve the purpose of freeing up money that can be used to fund Toyota’s shift to electric vehicles, they will also be used toward buybacks.

The unwinding of cross-shareholdings "means gradually turning them into viable assets,” Masahiro Yamamoto, chief officer of Toyota’s accounting group, said at the company’s results briefing in May.