The resignation of Mr Ma follows the departure of outspoken critics of SoftBank founder Masayoshi Son’s pivot towards a $100bn investment fund, including Fast Retailing chief executive Tadashi Yanai.
SoftBank is expected to report a $12.5bn annual operating loss — its biggest ever — when it publishes results later on Monday, as the market turmoil caused by the coronavirus outbreak wreaked havoc on some of the biggest bets made by its Saudi-backed technology fund.
Shares in SoftBank briefly rose 3 per cent as the company said it planned to buy back as much as ¥500bn ($4.7bn) of its own shares by March 2021, in the first tranche of a ¥2tn share buyback announced in March.
Mr Ma and Mr Son are close friends and have been business partners since the founder of SoftBank made his most successful investment in Alibaba in 2000. But the two Asian billionaires have taken separate paths, with Mr Ma retiring as executive chairman of the Chinese ecommerce group in September to focus on philanthropic projects in education.
Mr Ma warned in a panel conversation with Mr Son in December that included discussion about the Vision Fund that “too much money” inevitably leads to a “lot of mistakes”.
SoftBank said Mr Ma had asked to resign for “personal reasons”. Alibaba could not be immediately reached for comment.
In addition to Mr Yanai, Nidec founder Shigenobu Nagamori stepped down from SoftBank’s board three years ago. Power struggles inside the Vision Fund also led to the departure last year of Mark Schwartz, the company’s longtime independent director.
On Monday, SoftBank said it would add two new non-executive directors to its board: Lip-Bu Tan, founder of San Francisco-based venture capital fund Walden International and chief executive of Cadence Design Systems, and Yuko Kawamoto, a professor at Waseda Business School.
However, some analysts expressed reservations at the changes.
“We question whether these members would be able to challenge Son sufficiently to ensure good governance,” Lightstream Research analyst Mio Kato wrote in a note on research platform Smarkarma.
SoftBank’s stock has climbed 74 per cent since plunging to a four-year low of ¥2,687 on March 19, a sell-off that prompted Mr Son to unveil plans for a $41bn asset sale to reduce debt and launch the share buyback.