Sullivan & Cromwell and Davis Polk & Wardwell have the lead roles on an upcoming Tokyo initial public offering of Japanese conglomerate SoftBank Group Corp.’s domestic telecommunications business that seeks to raise $21 billion.

The proposed listing of subsidiary SoftBank Corp., slated for Dec. 19 on the Tokyo Stock Exchange, will be the largest the world has seen since Chinese e-commerce giant Alibaba Group Holding Ltd.’s $25 billion listing on the New York Stock Exchange in 2014.

The billions raised will fund SoftBank’s future investments and help lower the company’s ballooning debt, which, as of the end of September, was about $158 billion.

Sullivan & Cromwell Tokyo partners Keiji Hatano and Izumi Akai are representing SoftBank Corp. on its listing. In 2016, the New York firm advised SoftBank on a $10 billion sale of shares in Alibaba.

Mori Hamada & Matsumoto is advising the issuer on Japanese law, led by Tokyo partner Taro Omoto. The Japanese firm, alongside Morrison & Foerster, previously advised SoftBank Corp. on its $20 billion acquisition of American mobile carrier Sprint Nextel Corp. in 2012.

Davis Polk Tokyo partner Jon Gray is representing a group of underwriters led by Nomura Holdings Inc., Goldman Sachs Japan Co. Ltd., Mizuho Securities Co. Ltd., Deutsche Bank, JPMorgan and SMBC Nikko Securities Inc. In 2016, the U.S. firm, alongside Slaughter and May, advised U.K. chip designer ARM on its $31 billion sale to SoftBank.

Anderson Mori & Tomotsune is serving as Japanese counsel for the banks.

Japanese entrepreneur Masayoshi Son started SoftBank as a telecom carrier but has transformed the company into a global tech investor over the years. In addition to famously being an early investor in Alibaba, in 2016, Son’s SoftBank established, in cooperation with a Saudi Arabian sovereign fund, a $100 billion Vision Fund for technology investment around the world. Vision Fund portfolio companies include ARM, Indian e-commerce company Flipkart and shared office space provider WeWork Companies Inc.

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