The KOSPI's 17.91% surge to 6,595.45 on Friday was the index's biggest single-day gain in 46 years, topping October 2008's 11.95% record [1]. SK Hynix hit its +29.95% daily limit, and Samsung rose 26.81%. The session arrived on the same day new deposit rules for single-stock leveraged ETFs took effect.

The regulatory timing is the structural context MSM underplayed. Korea's new restrictions limit how much retail leverage can chase individual stocks, and the rules took effect during the session the market posted its all-time daily gain [2]. The record arrived despite — or because of — the constraint. The deposit rule change targets the speculative instruments that amplified retail participation in Korean semiconductor stocks.

By requiring higher margins for leveraged bets on single names, regulators aimed to moderate the volatility that characterized previous sessions [2]. The coincidence is the story: a regulatory tightening designed to cool speculative excess arrived on the same day the market produced its largest gain in nearly half a century. The rule did not prevent the surge; it may have shaped its composition.

For market structure watchers, the session raises a question about whether the new rules actually constrained speculative excess or merely redirected it. The KOSPI's gain was concentrated in semiconductor names — SK Hynix and Samsung — that are the primary targets of leveraged-ETF products. If the rules are working, the surge should reflect genuine institutional buying rather than retail leverage; if they are not, the next correction will test whether the constraint holds.

-- DAVID CHEN, Beijing