"It's part of me that may think (Son) is trying to make up for … mispricing in Softbank Corp.," he added, saying that the price of the domestic telecommunications unit's listing was "too high."  Repurchase comes after the SoftBank Group increased 2.35 trillion in December by listing about one third of the shares in SoftBank Corp, which on Tuesday reported a 24 per cent jump in quarterly earnings.
Beyond the announced share buyback, Dan Baker, an analyst at Morningstar, pointed to other possible causes for Thursday's strong gains.
One of them was that Softbank earnings were presented differently to mark "sum-of-the-party valuations instead of discussing results from some businesses, Sa Baker to CNBC in an email.
Baker also cited the additional details that surround Softbank's vision fund's performance and the use of hedging to lock the company's gains in chipmaker Nvidia as potential catalysts for Thurs
Softbank announced on Wednesday that it had dumped all its efforts, worth more than $ 3 billion, in Nvidia in January