On September 30, 2026, the Tokyo Stock Exchange closed sharply higher, with the Nikkei 225 up 1.94% at 66,753.50 points, led by buying in technology and semiconductor stocks. SoftBank Group (Tokyo Stock Exchange: 9984) stood out, jumping 6.55% to 6,430 yen per share.

The rally comes on the eve of a specific date. On February 27, 2026, SoftBank announced an additional $30 billion investment in OpenAI, split into three tranches of $10 billion each, which would bring the Japanese group’s cumulative exposure to about $64.6 billion and its stake to roughly 13% of OpenAI Group PBC. At the time, founder and CEO Masayoshi Son said:

«Artificial intelligence is transforming the world at an unprecedented speed [...] we have strong conviction in its continued growth»

while OpenAI CEO Sam Altman described SoftBank as

«the perfect long-term partner to maximize the benefits of AI on a global scale».

The first two tranches are done, the third is due October 1

The first two tranches, each worth $10 billion, were already executed on April 1 and July 1, 2026, through the subsidiary SoftBank Vision Fund 2. The third and final $10 billion tranche is scheduled for October 1, 2026, and it is this date that the market was looking at in the September 30 session.

To fund it, between September 21 and 29 SoftBank placed a bond offering totaling about $11.1 billion ($10 billion in U.S. dollar tranches maturing in 3.5, 5.5 and 7.5 years, plus €1 billion in euro tranches maturing in 4 and 6 years), with yields between 9% and 10% on the dollar tranches, consistent with the BB+ rating (sub-investment grade, or “junk”) assigned by Fitch Ratings.

According to early indications reported by intermediaries, investor demand exceeded $20 billion, almost double the amount offered. If confirmed in the final details, it would be the largest non-financial corporate bond issue ever completed in the Asia-Pacific region, ahead of the 7-Eleven offering of January 2021.

The contrast with South Korea

In the same session, the Seoul stock exchange moved in the opposite direction: the Kospi closed down 0.48% at 6,838.05 points. Samsung Electronics lost 1.47% to 268,500 won, while SK Hynix limited its losses (+0.62%).

In the third quarter, the Kospi fell 18.8%, one of the worst performances among the world’s major indexes, with the forward price-to-earnings (P/E) multiples of Samsung and SK Hynix compressed to 4-5 times earnings. The move reflects the unwinding of positions in the so-called “AI trade” that had supported the two memory-chip giants in the first part of the year.

The comparison shows how, within the same Asian tech sector, markets are rewarding different stories: in Tokyo, a direct bet on AI software through SoftBank/OpenAI; in Seoul, caution on memory-chip makers after months of gains.

Editor’s note

This article was originally published in Italian on money.it by Ufficio Studi Money.it on September 30, 2026 as «SoftBank vola a Tokyo (+6,5%) alla vigilia del terzo maxi-versamento da 10 miliardi per OpenAI». It has been translated and adapted for an international audience by the Money.it International desk.