South Korea KOSPI Plunges as Margin Calls Trigger Emergency Halts

South Korea’s KOSPI has plunged 13% in eight trading days, with trading paused by emergency circuit breakers twice in one week (June 8 and June 10). The selloff was driven by margin calls and the resulting forced selling across the market. Key stress indicators are worsening. Forced stock sales from margin calls reached about 300 billion won (~$197 million). Retail margin debt is near 38 trillion won (~$24.9 billion), leaving leveraged traders vulnerable to sharp, fast moves. KOSPI’s volatility also spiked, with a volatility index above 90 on Tuesday (record high). Market structure is amplifying the shock. Samsung and SK Hynix together account for more than half of the KOSPI weighting, and nearly 75% of its 2026 gains. This concentration limits downside support when these chip names face selling pressure. The put-call ratio on the KOSPI 200 hit 2.5, the highest in five years, signalling heavy demand for downside protection. For crypto traders, the main takeaway is liquidity and risk sentiment spillover: when margin calls force deleveraging in a major Asian market, it often tightens risk appetite regionally and can translate into higher volatility across correlated assets, including crypto.