Why KOSPI is getting crushed while Nikkei 225 keeps its weekly gain intact

Asian stocks traded cautiously on Friday, but the week exposed a widening gap between South Korea and Japan.

The KOSPI slipped 0.5% and headed for a 5% weekly loss, while the Nikkei 225 fell 0.9% yet remained on course to gain 1.2%.

Both markets are exposed to the AI hardware cycle, but Korea’s concentrated memory-chip trade has absorbed far more damage.

Investors are now waiting for US payrolls and watching another rise in oil prices, two forces that could determine whether the divergence narrows or deepens.

Korea’s chip concentration keeps the KOSPI under pressure

The KOSPI was set for a seventh consecutive weekly decline after Thursday’s 4.6% slump, when Samsung Electronics and SK Hynix fell 6.3% and 10.4%.

The retreat followed renewed selling in US storage and semiconductor shares, reviving doubts about how much AI-related growth is already reflected in valuations.

Korea’s vulnerability is partly structural. Samsung and SK Hynix represented about 53% of the KOSPI’s market value when the index crossed 9,000 in June.

Their gains helped the benchmark more than double in the first half, but the same concentration now magnifies every reversal in memory-chip sentiment.

Investors are also questioning capital allocation and whether record cash generation will translate into larger shareholder returns.

That leaves the KOSPI unusually sensitive to earnings guidance and shifts in Wall Street’s AI trade, even while demand for high-bandwidth memory remains strong.

Nikkei’s weekly gain masks a fragile exporter trade

The Nikkei 225 retained a weekly advance despite Friday’s decline, showing more resilience than Seoul. Even so, the weakness was concentrated in AI-linked names.

Lasertec dropped almost 10%, SoftBank Group lost more than 6% and Screen Holdings fell more than 4% in early trading as higher energy costs and semiconductor concerns weighed on sentiment.

The yen adds another source of tension. It traded near 158.5 per dollar after last week’s rare joint intervention by Japan and the US briefly drove it from above 163 to around 155.

A weaker currency supports exporters’ overseas earnings, but rapid depreciation lifts import costs and raises the risk of further official action.

The Nikkei is therefore caught between two opposing forces. Yen weakness helps large exporters, while intervention-driven strength can compress their earnings outlook.

Its weekly gain looks firmer than the KOSPI’s performance, but it remains vulnerable to a sharp move in US yields or the currency.

Payrolls and oil could decide the next leg

Economists expect the US economy to have added about 80,000 jobs in July after a 57,000 increase in June, with unemployment holding at 4.2%.

Futures markets placed the chance of a September Federal Reserve rate increase near 57% on Thursday, leaving the report capable of shifting bond yields and technology valuations.

JPMorgan economist Michael Feroli expects a strong number to be difficult for equities because it would reinforce the case for higher-for-longer rates.

A softer report could provide relief by pulling Treasury yields lower and reducing pressure on expensive growth stocks.

Brent rose 1% to $83.38 a barrel after gaining 3.8% on Thursday as renewed Houthi attacks and proposed Iranian restrictions on vessels in the Strait of Hormuz revived supply concerns.

Although crude remained down sharply for the week, a sustained rebound would increase costs for Japanese and Korean companies and complicate the inflation outlook.

For now, the KOSPI remains the clearer expression of stress in Asia’s AI trade.

The Nikkei is holding up better, but that cushion could disappear if payrolls lift yields, oil keeps climbing or the yen becomes disorderly again.