SoftBank Group's stock price reached a historic high on Monday, driven by market speculation that its holdings in OpenAI and SB Energy could yield substantial returns if they go public. According to Jin10, SoftBank's stock has surged 40% since May 20, with the company's market capitalization surpassing 40 trillion yen ($252 billion). The stock's sharp rise over two consecutive days last week followed reports that OpenAI is preparing to file for an IPO in the coming days. Additionally, SB Energy, a power infrastructure company, announced plans to confidentially file for an IPO in the United States. As OpenAI appears to be moving closer to an IPO, concerns about competitors like Anthropic, Google, and xAI threatening OpenAI's position have eased. Takashi Nakagawa, a senior analyst at TokaiTokyo Intelligence Laboratory, noted that the market is "extremely excited" about the long-anticipated OpenAI IPO potentially becoming a reality. He stated that this move would enhance transparency in the AI sector, which currently has relatively opaque valuations. SoftBank's investment portfolio includes a significant number of AI-driven, non-public startups.