SoftBank Group has completed the final installment of its additional investment in OpenAI, lifting its cumulative investment in the company to $64.6 billion.

Following the announcement, SoftBank's Tokyo-listed shares fell on Friday as the market continued to focus on the financing and balance sheet pressures stemming from the company's massive bet on artificial intelligence.

SoftBank said it has invested a further $10 billion in OpenAI through SoftBank Vision Fund 2, completing the $30 billion additional investment plan announced in February this year.

After the completion of this transaction, SoftBank's stake in OpenAI stands at approximately 13%.

The latest $10 billion investment was funded by foreign currency senior notes that SoftBank announced last week.

In other words, the company continues to raise capital through the capital markets to support its OpenAI investment.

Meanwhile, SoftBank is also unwinding the short-term financing arrangements previously set up for the OpenAI investment.

The company said it has cancelled, effective September 30, the remaining $10 billion undrawn portion of a $40 billion bridge loan.

After repaying part of the borrowing early earlier this month, all borrowings under this bridge loan have now been repaid in full, and no unused credit line remains.

This means SoftBank's transitional financing framework previously established for the OpenAI investment has come to an end, but long-term financing pressure has not disappeared as a result.

The latest $10 billion was still completed through newly issued foreign currency bonds, showing that the company's continued investment in AI still requires substantial external capital support.

This transaction further highlights SoftBank founder Masayoshi Son's aggressive bet on artificial intelligence.

OpenAI has become one of SoftBank's largest investments to date, and the cumulative $64.6 billion commitment has further elevated the importance of this investment to the group's overall asset allocation.

The market's primary concern is therefore not whether SoftBank remains bullish on OpenAI, but how much capital this AI bet will require and how many debt and other financing tools the company will need to support its expansion.

SoftBank's share price has also been continuously affected by this issue recently.

As the scale of AI investment continues to expand, investors are increasingly focused on future financing costs, the balance sheet's capacity to absorb them, and whether core assets such as OpenAI can generate sufficiently high returns to cover current commitments.

Therefore, SoftBank's completion of the final OpenAI additional investment is more of a milestone: the $30 billion additional investment has been fully completed, and cumulative investment has risen to $64.6 billion, but the core controversy surrounding SoftBank's AI strategy has become more concentrated — what will determine the value of this deal going forward is no longer the scale of investment, but whether OpenAI can generate sufficient returns and whether the financing costs SoftBank bears for it are manageable.