The Rally Was Over Before the Open · Semiconductors lifted the index; the rest moved the other way · KOSPI 6,894.23 +2.66% · KOSDAQ 827.12 +0.60%
2026.09.18
Snowshagal Daily
snowshagal.com

The Rally Was Over
Before the Open

TODAY IN ONE LINE Semiconductors lifted the index; the rest moved the other way
KOSPI6,894.23 +2.66%
KOSDAQ827.12 +0.60%
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SNOWSHAGAL · DAILY
MARKET RESEARCH
2026.09.18 · FRI
KRX CLOSE 15:30
DAILY MARKET NOTE / 18 SEP 2026

The Index Rose 2.66%,
Breadth Narrowed Further

KOSPI +2.66% · KOSDAQ +0.60% · foreigners turned net buyers for the first time in eight sessionsOf the 178.82-point gain, 170.29 points came from the opening gap · after U.S. semiconductors surged overnight, the Korean market opened at +2.54%412 stocks advanced versus 466 declined · despite the sharp index gain, market breadth narrowed from the previous sessionThe index was lifted by large-cap semiconductors · financial high-dividend names and shipbuilders moved the other way

When one pillar surges, it can make the whole market look higher.
MARKET PATH / 01

Most of the Closing Gain Was Already in Place at the Open

When did direction change, and what was working at the time?
KOSPI · 09:00~15:30Opened at 6,885.70 → 10:25 low 6,830.95 → 14:15 high 6,914.08 → closed at 6,894.23
09:00 12:00 15:30
OPEN6,885.70+2.54%
LOW6,830.95+1.72%
HIGH6,914.08+2.96%
CLOSE6,894.23+2.66%
THE READ

Of the day’s 178.82-point gain, 170.29 points came from the gap · only 8.53 points were added from open to closeThe intraday high-low range was 83.13 points · built between the 10:25 low and 14:15 high; the 8.53-point open-to-close net move was about 10% of that rangeEven the morning pullback never came close to closing the gap · no separate domestic catalyst emerged that was strong enough to reverse the overnight repricingThe fact that more stocks fell than rose while the index gained 178 points defines the character of the session

OPEN · MORNING

Opened 2.5% Higher, Then Hit the Day’s Low at 10:25

The market opened 170.29 points above the previous close · after U.S. semiconductors surged overnightBy the first 5-minute bar at 09:05, the index had already slipped into the 6,860s · the open was the morning highThe day’s low came at 10:25 at 6,830.95 · 54.75 points below the open but still 115.54 points above the previous close · less than one-third of the gap was retracedAt 09:48, Samsung Electronics was +2.77% and SK hynix +4.47% · semiconductors led from the start

AFTERNOON

Direction Turned After Noon, Reaching the Day’s High at 14:15

After the 10:25 low, the index traded narrowly around 6,850 through the 11 o’clock hourA stair-step rise came around 12:10 · by around 13:00 the index had reached the 6,898 areaThe day’s high was 6,914.08 at 14:15 · 83.13 points above the lowSK hynix closed +6.42% · SK Square +7.04% · while the index rose, shipbuilding and financial high-dividend names moved the other way

CLOSE

Closed 19.85 Points Below the High

After the high, the index pulled back to around 6,876 near 14:55, then recovered to 6,894.23 just before the closeThe close was 19.85 points below the day’s high and 63.28 points above the day’s lowKOSDAQ opened at 832.72, near its intraday high of 833.57, and closed below the open · a different shape from KOSPIKOSPI trading value rose sharply from the previous session to KRW 25.5633tn

Path read from the KRX regular-session KOSPI 5-minute chart · horizontal positions reflect actual times · line vertices are values read from the 5-minute chart, while only the open, high, low and close are official closing figures · the day’s low came in the 10:25 bar and the high in the 14:15 bar · the previous close of 6,715.41 was 115.54 points below the day’s low and therefore falls outside this chart’s vertical range.
WHY / 02

The Market Gapped Higher With U.S. Semiconductor Strength and Lower Long-Term Yields Already Known

Only the catalysts that actually explain the day’s direction
01

U.S. Semiconductors Moved First on Jensen Huang’s Sales Outlook; Korea Opened With a Gap

At a Scotland AI summit on September 17 local time, Nvidia CEO Jensen Huang said Nvidia’s chip sales next year would be twice this year’s levelIn the same U.S. session, the Philadelphia Semiconductor Index +3.14% · Micron +5.50% · SanDisk +6.21%At the same time, the U.S. 10-year yield fell below 5% and the rise in crude oil eased, helping risk appetite recoverKorea moved in the same direction: KOSPI Electrical & Electronics +4.46% · SK hynix +6.42% · Samsung Electronics +3.37%

+3.14%Philadelphia Semiconductor Index · Sept. 17 local time
Show evidence
U.S. session, Sept. 17 local time · Nasdaq 26,418.30 +1.69% · S&P 500 7,637.76 +1.14% · Dow 51,778.04 +0.61%
VIX fell 12.8% to 15.44 · risk aversion reversed on the first session after the Fed decision
U.S. 10-year yield closed at 4.947% · down from 5.006% the previous session, back below 5%
SK hynix ADR +4.64% · Nvidia +2.54%
Next-generation product read-through · Vera Rubin is expected to use HBM4 and Rubin Ultra HBM4E, leading analysts to link stronger chip sales to a faster transition into next-generation high-bandwidth memory
The opposing view was also raised · if production is concentrated on high-bandwidth memory, conventional DRAM supply could tighten further, worsening imbalances across the memory market
Domestic data · August PPI rose 0.2% month-on-month, returning to an increase after one month · +7.9% year-on-year · heat-driven agricultural prices and global oil prices were cited as reasons
MONEY / 03

Foreigners Turned Buyers for the First Time in Eight Sessions — and Bought SK hynix

Who moved today’s index
FOREIGN · KOSPI CASH
+KRW 421.2bn

Foreigners turned net buyers for the first time in eight sessions · the reversal itself was today’s key flow eventYet SK hynix alone ranked No. 1 in foreign net buying, while the same foreign investors made Samsung Electronics their No. 1 net sellThe net buying amounted to only around KRW 400bn, small relative to what foreigners sold over the previous seven sessions

Top net buySK hynix
Top net sellSamsung Electronics
Flow details
KOSPI trading valueKRW 25.5633tn
KOSPI 200 Foreigners+KRW 1.5270tn
KOSPI 200 futures · institutions-KRW 1.3280tn
KOSDAQ foreigners-KRW 44.0bn
Stock-level flow amounts vary by classification, so only rankings and concentration direction are shown · SK hynix ranked No. 1 both among foreign net buys and retail net sells, while Samsung Electronics was the top institutional net buy
Foreigners, who returned to net buying in KOSPI cash, moved in the same direction in KOSPI 200 futures · but cash and futures are different markets, so neither is used as evidence for the other
KOSDAQ by investor · institutions +KRW 22.0bn net buy · retail +KRW 12.0bn net buy · foreigners -KRW 44.0bn net sell · all three flows were only in the tens of billions of won
USD/KRW at Hana Bank’s 15:30 transaction base rate: KRW 1,382.0 per dollar · up KRW 0.3 from 1,381.7 in the previous session
SECTOR / 04

Strong · weak

Today’s distribution of strength, not just a ranking

Strength was in semiconductors and AI power infrastructure; outside the index, more stocks actually fell than rose.Only 10 of 24 KOSPI sectors rose and 14 fell, yet the index gained +2.66%Electrical & Electronics and Manufacturing were the top two KOSPI sectors; every other advancing sector gained less than 2%Shipbuilding, strong in the previous session, reversed lower after one day · financial high-dividend themes and some large financials, including KB Financial and Shinhan Financial Group, were weak

STRONG

KRX-Akros AI Power InfrastructureTheme+6.45%
KRX K-AI Semiconductor TOP2+Theme+5.07%
Electrical & ElectronicsKOSPI sector+4.46%
ManufacturingKOSPI sector+3.42%

WEAK

KRX Shipbuilding TOP10Theme-2.11%
PharmaceuticalsKOSDAQ sector-2.05%
KOSPI 200 Financial High Dividend TOP 10Theme-1.85%
Electricity & GasKOSPI sector-1.02%
Sector evidence
Of 46 KRX industry indices, 23 rose and 23 fell · of 24 KOSPI sectors, 10 rose · of 22 KOSDAQ sectors, 13 rose
Of 39 theme indices, 23 rose and 16 fell · KRX Semiconductor Top 15 +3.25% · KRX AI Semiconductor +2.42%
Seven of the top 10 stocks by market cap rose · SK Square +7.04% · SK hynix +6.42% · Samsung Electro-Mechanics +4.36% · Samsung Electronics +3.37% · Samsung Electronics Pref. +1.45% · Hyundai Motor +0.55% · Samsung Biologics +0.14%
The three decliners in the same group · KB Financial -2.40% · Samsung C&T -1.27% · LG Energy Solution -0.27% · Shinhan Financial Group also fell -2.82%
No common same-day catalyst was separately confirmed for the weakness in financials, so no causal explanation is attached · the KOSPI Financials sector index itself rose +0.26%, showing mixed direction within the group
Advancers and decliners · KOSPI: 5 limit-up · 407 up · 41 unchanged · 465 down · 1 limit-down · KOSDAQ: 3 limit-up · 919 up · 116 unchanged · 698 down · 2 limit-down
Advancing-stock ratio · KOSPI 44.8% (412/919) · KOSDAQ 53.0% (922/1,738) · numerator = advancers + limit-up stocks; denominator = limit-up + up + unchanged + down + limit-down
Sector returns are market-cap-weighted index returns, not sector-level net inflows
CHANGE / 05

Answers to Yesterday’s Questions

Scoring yesterday’s conditions today
YESTERDAY → TODAY

All three questions were answered in one day · the U.S. 10-year fell back below 5%, foreigners broke a seven-session selling streak with their first net-buying day in eight sessions, and shipbuilding’s strength lasted just one dayThe three conditions simply changed direction on the same day · today’s data provide no basis for saying any one of them drove the othersBut the advancing-stock ratio narrowed from 49.7% to 44.8%, so market breadth moved the opposite way on a day when the index rose sharply

01
U.S. 10-year yield · close
5.006%
→
4.947%
02
Foreign KOSPI cash flow
7 sessions of selling
→
Turned to buying
03
KRX Shipbuilding TOP10
+5.39%
→
-2.11%
NEXT / 06

What to Watch Next Session

Conditions that can actually be scored, not probabilities
Do foreign net purchases continue for a second day?

Today was the first net-buying session in eight sessions · the amount was only in the KRW 400bn range, small versus the preceding selling · score it on the sign of the next session · if it ends after one day, a sustained turn to buying has not been confirmed

Does KOSPI’s advancing-stock ratio move above 50%?

It narrowed to 44.8% today from 49.7% in the previous session · even if the index rises again, a ratio below 50% would mean the structure of one semiconductor pillar carrying the index remains intact · KOSDAQ was 53.0%

Does the U.S. 10-year yield post a second close below 5%?

Sept. 17 local close: 4.947% · score it on the next close · a move back above 5% would revive the rate pressure seen through the previous session

Yesterday the index stood still while the market moved; today was the reverse.

Full index, FX, rates and commodity data are in MARKETThe Daily keeps only the numbers needed to explain today’s session.
MARKET ↗
Sources · data basis
Reference date: 2026.09.18 · index, sector, theme and individual-stock closes use the KRX regular session, 09:00–15:30
Information cutoff: Sept. 18, 20:00 KST · indicator results and overseas intraday values released after that time are not included
Indices · KOSPI open 6,885.70 · low 6,830.95 · high 6,914.08 · close 6,894.23 are official regular-session closing figures · KOSDAQ closed at 827.12; open 832.72 · high 833.57 · low 824.73
Intraday chart · path read from the KRX regular-session KOSPI 5-minute chart; horizontal positions reflect actual times · the day’s low was the 10:25 bar · the day’s high was the 14:15 bar · Samsung Electronics +2.77% and SK hynix +4.47% at 09:48 are quoted from intraday reporting
Investor totals · KRX regular-session closing tally · 15:38 · KOSPI foreigners +KRW 421.2bn · institutions +KRW 1.5054tn · retail -KRW 3.5869tn · Other corporations are not included in this tally, and no residual is back-solved from the three values · closing reports based on cumulative KRX + NXT trading differ at foreigners +KRW 977.3bn · institutions +KRW 1.7168tn · retail -KRW 4.3719tn; these are not mixed into the body · KOSDAQ institutions +KRW 22.0bn · retail +KRW 12.0bn · foreigners -KRW 44.0bn
Stock-level flows · KRX trading by investor · because collection time was after the regular-session close, only rankings and concentration direction are shown; amounts and ratios are omitted
Futures · KOSPI 200 futures by investor use the 16:20 final tally
Trading value · KOSPI KRW 25.5633tn quoted from closing reports
Market breadth · KRX counts of stocks by price move · limit-up is counted separately from ordinary advancers · numerator of the advancing-stock ratio = advancers + limit-up; denominator = limit-up + up + unchanged + down + limit-down
Sectors · themes · KRX Index: 46 industry indices and 39 theme indices at the close
Previous domestic session · Sept. 17 KOSPI close 6,715.41 · advancing-stock ratio 49.7% · KRX Shipbuilding TOP10 +5.39% · seven consecutive sessions of foreign net selling as stated in the Sept. 17 issue
Overseas · Nasdaq 26,418.30 · S&P 500 7,637.76 · Dow 51,778.04 · Philadelphia Semiconductor Index 11,599.49 · VIX 15.44 are Sept. 17 local closes · Micron +5.50% · SanDisk +6.21% · Nvidia +2.54% · SK hynix ADR +4.64% quoted from reports
Rates · U.S. 10-year close 4.947% is an internally collected value (^TNX, Sept. 17 local close), on the same basis as the previous session’s 5.006%
Companies · Jensen Huang’s remarks are from the Sept. 17 local-time Scotland AI summit · plans for HBM in Vera Rubin and Rubin Ultra, and concerns about conventional DRAM supply, are cited from securities-industry commentary
Data · Korea’s August PPI was released by the Bank of Korea at 06:00 on Sept. 18 · +0.2% month-on-month · +7.9% year-on-year
FX · USD/KRW is Hana Bank’s 15:30 transaction base rate of KRW 1,382.0 per dollar · up KRW 0.3 from the previous session’s same base rate of 1,381.7
Schedule · U.S. equities open at 22:30 KST on Sept. 18 · the next Korean trading day is Sept. 21 · U.S. Q2 International Transactions and International Investment Position are confirmed on the BEA release schedule for Sept. 24, 08:30 local time
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