Week in Review: Nikkei +2.93%, TOPIX −0.91%—The AI Rally Hid a Weaker Broad Market

01Market Snapshot

Data checked: 2026-10-03 11:15 JST / 2026-10-02 19:15 PDT

Oct. 2 Nikkei	68,309.46 · −0.94% final close
Oct. 2 TOPIX	4,091.00 · about −1.0% public final close
Nikkei week	+2.93% · Sep. 25 close 66,364.20 → Oct. 2 close 68,309.46
TOPIX week	−0.91% · Sep. 25 close 4,128.59 → Oct. 2 close 4,091.00
USD/JPY	about 157.85 · Oct. 2 public close area
10Y JGB	about 3.099% · Oct. 2 public close
U.S. Oct. 2	S&P 500 +0.73% · Nasdaq +1.19% · Dow +0.49% final closes
Europe Oct. 2	STOXX 600 +0.8% final close

Mood: the most useful weekly number was not +2.93% by itself. It was the roughly 3.8-percentage-point performance gap between the Nikkei and TOPIX, showing how much concentrated AI-chip leadership distorted the headline.

02What Moved Tokyo

The week began with broad risk reduction. Ex-dividend effects, high global yields, oil and geopolitical risk all weighed on Monday and Tuesday. On September 29, TOPIX lost 1.72% and Prime Market breadth was decisively negative—weakness too broad to dismiss as a handful of Nikkei heavyweights.

The turn came Wednesday. AI and semiconductor names rebounded, lifting the Nikkei 1.94% and TOPIX 1.67%. Then Thursday’s Micron results and outlook intensified the AI-memory story, sending money into Advantest, Tokyo Electron, Kioxia and related suppliers. The Nikkei surged 3.30%, but TOPIX gained only 0.57%.

Friday exposed the other side of that narrow rally. The Nikkei lost 0.94%. SoftBank Group fell 5.83%, Nissan Motor 4.97% and Terumo 4.59%. Yet selective AI-infrastructure buying survived: Resonac gained 8.71% and Furukawa Electric 7.68%.

Date	Nikkei	Daily	TOPIX	Daily	Read
Mon Sep 28	65,877.62	−0.73%	4,112.00	−0.40%	Early gains faded as ex-dividend effects and higher rates weighed.
Tue Sep 29	65,481.27	−0.60%	4,041.13	−1.72%	Broad de-risking; Prime Market breadth was decisively negative.
Wed Sep 30	66,753.72	+1.94%	4,108.65	+1.67%	AI and chip shares rebounded and repaired much of Tuesday’s loss.
Thu Oct 1	68,956.72	+3.30%	4,131.98	+0.57%	Micron-driven AI/chip surge; Nikkei far stronger than TOPIX.
Fri Oct 2	68,309.46	−0.94%	4,091.00	about −1.0%	Profit-taking plus Tokyo CPI, oil and rate caution.

03Today’s Market Mover

AI semiconductor complex / Advantest (6857)

The week’s defining mover was not simply one Friday winner. It was the structure of AI-chip leadership pulling the Nikkei away from the broad market. On October 1, Advantest closed at ¥37,610, up 9.78%, as Micron’s results reinforced expectations for AI-memory demand and semiconductor test intensity.

The broader lesson is the TOPIX weekly decline. AI demand can be a real industrial investment cycle without automatically improving the outlook for every Japanese company. A 3% JGB, expensive energy and domestic inflation create a very different earnings backdrop for real estate, consumers, importers and highly valued growth stocks.

Confidence: High

04Sector Pulse

Leaders: AI semiconductor testing, fabrication equipment, memory, electronic components, optical connectivity and power infrastructure.

Weakness: broad de-risking dominated early in the week; Friday profit-taking hit major technology, auto and healthcare names.

Key signal: only 11 of the TSE’s 33 industry groups rose on October 1 even as the Nikkei gained 3.30%. The headline was much stronger than the tape.

05Yen Watch

USD/JPY spent most of the week in the 157s, briefly moving into the 158s on Thursday before softer U.S. payrolls weakened the dollar Friday. Public closing data put the pair around 157.85.

A stable 157–158 yen can still support translated exporter earnings, but with Brent above $100 it does not neutralize Japan’s imported energy burden. This week required reading the yen together with oil and JGBs rather than treating currency weakness as an automatic equity positive.

06Rates / JGB Watch

The 10-year JGB yield began the week near 3.09% and ended Friday around 3.099% on public market data. It briefly eased toward 3.05% as global bonds rallied, but the more important fact is that 3% itself is becoming normal market territory.

That changes Japan’s internal pricing. Banks and insurers can benefit from wider lending and reinvestment spreads, while mortgages, corporate funding, government interest costs, real estate values and high-multiple equities face a less forgiving discount rate.

07Global Handoff

Friday’s U.S. jobs report materially improved the next-open setup. September nonfarm payrolls rose only 29,000 versus 90,000 expected, and unemployment edged up to 4.2%. Traders sharply reduced expectations for another Fed hike in October.

The S&P 500 rose 0.73%, Nasdaq 1.19% and Dow 0.49%. Europe’s STOXX 600 recovered 0.8%. For Tokyo, that is supportive for AI and rate-sensitive growth shares after Friday’s profit-taking.

But the global handoff is not clean. U.S. 10-year yields touched 5.34% during the week, and Brent remained above $100, around $102.77 in Friday public reporting. Easier Fed expectations coexist with expensive capital and expensive energy.

08Policy / BOJ Watch

Tokyo September CPI rose 2.7% year on year both at the headline and core levels, while the measure excluding fresh food and energy reached 3.0%. Core inflation accelerated sharply from 1.8% in August.

Japan’s August unemployment rate was 2.5%, offering no major labor-market deterioration to force the BOJ away from normalization. The next BOJ meeting on October 29–30 remains the key domestic policy checkpoint.

09Publisher’s Market Note

The most interesting number this week was not the Nikkei’s +2.93%. It was TOPIX at −0.91%. The two indexes looked at the same Tokyo market and told nearly opposite stories. AI is a real Japanese investment theme—memory, power, testing, optical links and factories—but so are 3% government bonds, $100 oil and household inflation. Japan is becoming a market of several realities running at once, not one simple bullish story. — Bradley L. Bartz

10Before the Next Open

Can Tokyo inherit Friday’s U.S. rally? Watch the AI and semiconductor heavyweights first.
USD/JPY in the high 157s: a break toward 157 or a return to 158 changes the exporter setup.
10-year JGB around 3%: does the global bond relief persist, or does domestic CPI pull yields higher again?
Brent above $100: Japan remains directly exposed through imports, margins and household inflation.
Breadth: watch TOPIX, Prime advancers/decliners, banks and domestic-demand shares—not only the Nikkei.

11Sources and Method

Only public information was used. No paid article text was copied or reproduced. Equity figures are final Tokyo closes; FX, bond and overseas figures are labeled by date and confirmation status. Market data can be delayed depending on the source. This is original Japan.co.jp market journalism, not investment advice.

Nikkei Indexes — Nikkei 225 Japan Exchange Group — TOPIX Bank of Japan Statistics Bureau of Japan — CPI Ministry of Finance Japan

12Archive Entry

Date	2026-10-03
Report URL JP	/japan-market-desk/report-2026-10-03.html
Report URL EN	/e/japan-market-desk/report-2026-10-03.html
Market Mover	AI semiconductor complex / Advantest
Ticker	6857
Theme	AI chips · narrow Nikkei leadership · 3% JGBs · Tokyo CPI · yen
One-Line Reason	Micron-fueled AI demand drove a Thursday chip surge that lifted the Nikkei for the week even as TOPIX finished lower.
Nikkei Direction	Up +2.93% weekly
TOPIX Direction	Down −0.91% weekly
Production Window	Weekend week-in-review / before next Tokyo open
Data Checked	2026-10-03 11:15 JST / 2026-10-02 19:15 PDT