South Korean investors have increased borrowing to buy domestic shares as the market rebounds from recent lows. Margin debt reached 30.93 trillion won, or $21.9 billion, as of Thursday, up from 27.44 trillion won on Aug. 3, according to data compiled by KOFIA, the Korea Financial Investment Association. The rise came as heavyweight stocks including Samsung Electronics and SK hynix recovered sharply after volatility linked to concerns over the profitability of AI-related investment. Analysts said the easing of those worries suggests the market shows no immediate sign of cooling, and Kim Dong-won, an analyst at KB Securities, said investors are cautiously betting chipmakers will be rerated from the third quarter of the year.