KOSPI Surges Record 17.91% in One Session as Foreign Buyers Return — Retail Investors Sell ₩8.28 Trillion

The Quick Take

• The KOSPI surged 17.91% (over 1,000 points) in a single session on July 31, its largest single-day gain in history, driven by a US semiconductor stock rally.
• Foreign investors piled into Korean equities, but domestic retail investors ("개미") sold a record ₩8.28 trillion worth of stock — their largest daily net sale ever.
• Despite the record KOSPI surge, fear sentiment among individual investors remained elevated; some had cancelled vacations after losing ₩10 million in the prior month's sell-off.
• Seoul apartment trading showed price polarisation: 80%+ of July transactions were in apartments priced below ₩1.5 billion, while the ultra-premium ₩10 billion+ segment hit record highs.

The KOSPI index recorded its highest single-session percentage gain in history on July 31, 2026, surging 17.91% — over 1,000 index points — following a powerful rally in US semiconductor stocks in New York trading. Foreign institutional investors drove the rebound, accumulating Korean equities on what they assessed as deeply oversold levels after a 1,162-point three-day decline. However, the record surge was met with mass selling by domestic retail investors, who net-sold a historic ₩8.28 trillion of Korean equities in a single session. The divergence between foreign institutional buying and domestic retail selling captures the prevailing fear psychology in a market that had lost the equivalent of a month's savings for many individual investors in the preceding weeks.

The KOSPI surge carries immediate implications for Korean technology and semiconductor stocks, particularly those in the Samsung Electronics and SK Hynix supply chains, whose valuations are highly correlated with US peer movements in TSMC, Micron, and Nvidia. The scale of foreign inflows (and domestic outflows) also highlights a structural characteristic of the Korean equity market: retail investors, who hold a disproportionate share of Korean equities relative to developed-market peers, tend to sell into volatile recoveries rather than hold, which dampens the sustainability of rally moves. Separately, Seoul's apartment market showed wealth-driven polarisation — the mortgage-limited sub-₩1.5B segment accounted for 80%+ of transactions, while the ₩10B+ ultra-premium tier recorded new price highs driven by asset-rich buyers who are not mortgage-constrained.

The forward signals to watch are the sustainability of the KOSPI recovery above its pre-sell-off levels, the pace at which foreign institutional buying continues, and whether retail investor sentiment recovers from what survey data described as extreme fear following ₩10 million+ individual losses. Samsung Electronics' and SK Hynix's next earnings updates will be key catalysts, as the Korean semiconductor sector's earnings trajectory directly underpins any sustained KOSPI re-rating. The macro variable is the US semiconductor sector momentum: Korean equity markets have a historically high beta to US chip stocks, and any reversal in Nvidia, TSMC, or AMD would translate rapidly back into KOSPI selling pressure. The Seoul property polarisation thesis will be tested if the government implements the discussed property holding tax (보유세) increases on premium apartments.

Synthesized from 6 sources.