TOKYO (AP) — Japanese technology giant SoftBank Group and OpenAI stepped up their AI partnership Monday, setting up a 50-50 held company called SB OpenAI Japan. SoftBank Chief Masayoshi Son and OpenAI Chief Sam Altman appeared at an event in Tokyo, talking up their collaboration and inviting Japanese companies to join. Son, holding a shiny blue crystal ball as a symbolic prop, said its AI service Cristal could be used by companies for planning, marketing, emails and figuring out old source codes. Cristal will first roll out in Son’s own SoftBank Group companies, which include Arm, a semiconductor and software…