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.