The CEO of investment giant SoftBank Group recorded $81.4 billion in net worth on Wednesday, up 30% from the end of August, according to real-time data from Forbes.

The wealth surge followed the increase of SoftBank shares, having risen 24% in a month and 48% since the beginning of the year.

The recent launch of OpenAI’s newest model, GPT-6 Astra, designed for more complex work, has boosted investors’ confidence in SoftBank, which announced a $30-billion investment into the AI giant in February.

Along with previous investment, by October-end, SoftBank’s total funding in OpenAI will likely reach over $64 billion.

SoftBank also benefited from the gain of Arm Holdings, the British chip design company, which has also gained from the AI boom. Its shares have surged 128% year-to-date.

The jump in these assets have boosted Son up in the global ranking. He is now positioned 28th globally, compared to 36th in March when Forbes released its annual world’s billionaire list.

Son’s asset expansion, however, bucked the trend among Japanese richest billionaires. All four billionaires ranking behind him saw wealth decline in the last nine days.

SoftBank CEO Masayoshi Son. Photo by Reuters

Tadashi Yanai, CEO of founder and president of Fast Retailing, the company behind fashion brand Uniqlo, saw net worth drop $2.8 billion to $59.6 billion in the period.

Takemitsu Takizaki, honorary chairman of sensor producer Keyence, saw fortunes shrink by $1.5 billion to $23.2 billion.

The fourth and fifth richest individuals, Yasumitsu Shigeta and Takao Yasuda, each posted a $200 million decline in wealth. They now control $6.2 billion and $4.2 billion assets, respectively.

The declines, however, are likely short-lived. Japan's benchmark Nikkei 225 has fallen about 2.7% over the past month, but remains up over 26% this year.

The 2026 outlook for the Nikkei 225 remains bullish. A survey of 10 Japanese financial institutions in August found forecasts for year-end at around 75,000 points, up 15% from the current level.