[Nikkei Recap] Sep 14, 2026: Nikkei 225 Falls 518 Points to 63,493 as SoftBank Group Plunges on AI Slowdown Fears

Hey everyone, Hirokichi here.

Tokyo stocks fell again on September 14, 2026. The Nikkei 225 closed at 63,492.99, down 518.35 points (-0.81%) from the previous week’s close. SoftBank Group plunged more than 13% at one point during the session and dragged the Nikkei down on its own, while the broader TOPIX and the Tokyo Stock Exchange Growth Market 250 Index both finished in positive territory. It was a day where the headline number and the underlying market told two different stories.
Let’s look at what happened today, why the indexes pulled in opposite directions, and which stocks got the most attention.

Today’s index moves

First, here’s how the major indexes closed.

As this table shows, the Nikkei 225 was the only index in the red — TOPIX and the Growth 250 both closed higher. The Nikkei 225 is a price-weighted index, which means stocks trading at a high per-share price (often called “heavyweight” or “high-priced” stocks) have an outsized effect on the index, regardless of the company’s actual market value. As I’ll explain below, a handful of stocks like SoftBank Group fell hard and single-handedly dragged the Nikkei down, even though more Tokyo Stock Exchange Prime Market stocks rose than fell on the day. The yen was trading around 154.20 to the dollar, a touch weaker than the previous close.

Why did the market move? The three factors behind today’s session

Today’s price action can be broken down into three main factors.

(1) Reports that OpenAI’s leadership is planning to postpone its initial public offering (IPO) within 2026. SoftBank Group, which has poured a massive amount of capital into OpenAI, took a direct hit and fell more than 13% intraday. Concerns spread that the pace of AI development itself might be slowing, and the selling spread to semiconductor-related stocks more broadly.

(2) Growing expectations of an early U.S. rate hike. The U.S. Consumer Price Index (CPI) released the previous Friday (the 11th) showed accelerating inflation, which strengthened rate-hike expectations. When interest rates rise, the discount rate used to value future profits in today’s terms also rises, so high-P/E (price-to-earnings ratio) tech and semiconductor stocks tend to look more expensive by comparison.

(3) Lingering concern over tensions in the Middle East. Geopolitical risk continued to simmer in the background and weighed on investor sentiment.

For context, U.S. markets rallied the previous Friday (the 11th) as an oil price pullback lifted risk appetite: the Dow Jones Industrial Average closed up 509.19 points (+0.98%) at 52,573.29, the Nasdaq Composite rose 251.31 points to 26,333.04, and the S&P 500 gained 65.28 points (+0.86%) to close at 7,656.98. That U.S. strength gave some support to Tokyo at the open, but selling concentrated in heavyweight stocks with a large index weighting kept a lid on the Nikkei 225 for the rest of the session.

Stocks in the spotlight today, and why

This table shows the same story in numbers: AI-related selling hit heavyweight semiconductor and AI names like SoftBank Group, Advantest, and Kioxia, while capital rotated into SaaS names like Money Forward and into stocks with their own company-specific catalysts, like Kobe Bussan.

SoftBank Group (9984)

SoftBank Group closed down ¥701 at ¥5,839 (-10.72%), after falling more than 13% at one point during the morning session. The trigger was a report that the head of OpenAI, in which SoftBank has invested heavily, is planning to postpone the company’s IPO within 2026. In my view, SoftBank Group’s share price has been partly propped up by expectations of just how high OpenAI’s valuation could eventually climb, so a setback to those IPO expectations was bound to hit the stock hard.

Advantest (6857) and Kioxia Holdings (285A)

Semiconductor test equipment maker Advantest closed down ¥640 at ¥31,080 (-2.02%), while memory chipmaker Kioxia Holdings closed down ¥3,440 at ¥50,590 (-6.37%). Both are also high-priced, heavyweight stocks within the Nikkei 225, and together with SoftBank Group they were the biggest drags on the index today. When concerns about slowing AI development spread, expectations for AI-related chip demand tend to fade by association, and stocks tied to the same theme often get sold off together.

Money Forward (3994)

On the other hand, cloud accounting and household finance service provider Money Forward jumped ¥424 to close at ¥6,365 (+7.14%). As money flowed out of AI-heavy names, some investors apparently viewed a slowdown in AI development as a positive for SaaS (cloud software) companies outside the AI spotlight, and capital rotated in that direction. I find it interesting that the exact same piece of news — AI development slowing down — can be read as bad news for one stock and good news for another, depending on the business model.

Kobe Bussan (3038)

Kobe Bussan, which operates the “Business Supermarket” discount grocery chain, rebounded, closing up ¥201.50 at ¥3,167.0 (+6.79%). The rally came after the company reported higher operating profit for the May-July 2026 quarter. Since the market had reportedly been bracing for weaker results, the relief that the numbers weren’t as bad as feared appears to have driven the buying.

What this means if you’re an individual investor

If you’re dollar-cost averaging into index funds, there’s no need to get worked up over a single day’s move like today. It’s worth remembering that while the Nikkei 225 fell, both TOPIX and the Growth 250 actually finished higher — the market as a whole didn’t collapse. Getting into the habit of checking what’s actually happening beneath a headline number, rather than reacting to “stocks fell” at face value, will help you stay calm when these kinds of index-level distortions occur.

If you trade individual stocks, today looked like the kind of pullback that happens after money has piled heavily into a single theme — in this case, AI. Whether you see the sharp declines in stocks like SoftBank Group and Advantest as a buying opportunity or a reason to stay on the sidelines until the picture is clearer is a matter of judgment. Personally, I lean toward waiting until the full picture around OpenAI’s IPO plans becomes clearer rather than jumping in while the situation is still unsettled.

What to watch going forward

Here are three things worth keeping an eye on in the sessions ahead.

(1) Further news on OpenAI’s IPO plans. Whether the delay gets officially confirmed, or whether the reports turn out to be overstated, will likely drive the next moves in SoftBank Group and other AI-related names.

(2) U.S. monetary policy signals. With the FOMC (the Federal Open Market Committee, which sets U.S. monetary policy) meeting ahead, any data releases pointing to the direction of interest rates could easily spark fresh volatility in tech and semiconductor stocks.

(3) The situation in the Middle East. An easing of tensions would likely support investor sentiment, while further escalation could weigh on Japanese stocks through higher resource prices.

Let’s keep at it, slow and steady. See you tomorrow!

* This article is for informational purposes only and does not recommend any specific investment. Please make investment decisions at your own responsibility.

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