The index rose 159.10 points or 2.5 percent to 6,630.27 points shortly after the day's trading began.
That recovered about two-fifths of the previous session's 398.66-point plunge, when the main index in Seoul fell 5.8 percent and the Korea Exchange triggered a sidecar, a five-minute halt on program sell orders imposed when KOSPI 200 futures fall 5 percent or more.
SK hynix traded at 1,592,000 won, up 92,000 won or 6.1 percent after plunging 9.8 percent in the previous session. Samsung Electronics rose 3.0 percent to 255,000 won.
SK hynix said the previous day that its board had approved the repurchase and cancellation of 24.07 million shares or about 3.3 percent of its outstanding shares, in what the company called the largest treasury share cancellation by a listed Korean company. The buyback will run from Thursday through Nov. 19.
The chipmaker also vowed to return more than 50 percent of its cumulative free cash flow to shareholders from 2025 to 2027, up from the previous ceiling of 50 percent.
The announcement came after a sell-off that had erased roughly half of the stock's market value since its late-June peak.
Foreign investors were not the ones buying. They sold a net 188.0 billion won ($135 million) of main-board shares in the opening minutes, and institutions sold a net 250.1 billion won ($180 million). Individuals bought a net 405.1 billion won ($292 million).
The rebound was also narrow. Samsung Electro-Mechanics fell 2.9 percent to 1,347,000 won ($970), KB Financial Group lost 2.5 percent to 162,300 won ($117) and Hyundai Motor slipped 0.7 percent to 411,000 won ($296).
The junior KOSDAQ rose 15.73 points or 1.9 percent to 840.19.
Biotechnology was among the strongest sectors on the junior market, rising 5.7 percent after Moderna shares closed nearly 177 percent higher in New York on positive late-stage clinical trial data for a personalized melanoma vaccine developed with Merck.
The Nikkei 225 in Tokyo was up 0.7 percent at 65,810.95, snapping two straight losing sessions.
The won traded at 1,388.30 per dollar, slightly stronger than the previous day.
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