South Korea's highest-return stock investors rotated back into SK hynix and K-beauty earnings winners on Aug. 12, with Mirae Asset Securities data showing the chipmaker as the biggest net buy among the brokerage's top 1% of clients by one-month return as of 11 a.m. SK hynix traded at 1.49 million won, up 4.28%, as resilient U.S. semiconductor signals, including a 0.87% rise in the Philadelphia Semiconductor Index, a 0.84% gain in Micron, and after-hours jumps of more than 13% in CoreWeave and more than 6% in Super Micro, reinforced expectations that AI infrastructure demand would persist. Net buying also concentrated in Kolmar Korea, Silicon2 and Cosmax after stronger-than-expected second-quarter results: Kolmar Korea rose 15.71% after reporting 110.3 billion won in operating profit and a record 861.3 billion won in revenue, Silicon2 jumped 17.23% after posting 83 billion won in operating profit and 402.6 billion won in revenue, and Cosmax surged 25.39% after record quarterly sales and profit while its U.S. subsidiary delivered its first operating profit. Samsung Electronics led net selling despite gaining 6.47% to 255,000 won, highlighting profit-taking, while Samsung Electronics preferred shares ranked ninth in net buying. The KOSPI was at 6,567.40, up 3.50%, with foreign and institutional investors net buyers, while the KOSDAQ slipped 0.27%; the reversal from Aug. 11, when SK hynix and Samsung Electronics had topped net selling, underscored fast rotation in earnings-season trades.