SoftBank CEO Masayoshi Son and OpenAI CEO Sam Altman attend an event to pitch AI for businesses in Tokyo, Japan Feb. 3, 2025. Kim Kyung-Hoon | ReutersSoftBank posted a $2.4 billion gain at its Vision Fund in the December quarter as a jump in the value of its OpenAI investment helped offset losses in some of its other bets. The Japanese giant said it made a $4.2 billion gain on the value of its OpenAI investment in its fiscal third quarter, which runs to the end of December, offsetting losses ste...