After years of acquisitions saddled SoftBank Group Corp. with record debt and weighed down its stock, founder Masayoshi Son is getting serious about improving the company's balance sheet.

SoftBank has announced a series of asset sales as part of a broader effort to re-examine its technology portfolio, reduce its massive debt load and gain flexibility for future investments.

The company plans to raise $10 billion (about ¥1 trillion) from selling down its stake in China's Alibaba Group Holding Ltd. and another ¥73 billion ($685 million) from offloading shares in GungHo Online Entertainment Inc. It's also in discussions to exit Finnish game developer Supercell Oy, according to people familiar with the matter, a deal that could increase the amount raised via asset sales to $14 billion.