“This isn’t a stock market driven by corporate fundamentals anymore. It’s basically a coin toss.” This was one investor’s verdict on X (formerly Twitter) after one of the most extraordinary weeks in Korean stock market history. On Friday, the benchmark KOSPI surged 17.91 percent, or 1,001.89 points, to 6,595.45 — its largest one-day gain on record — after three consecutive sessions of losses. The rally was fueled largely by a sharp rebound in Samsung Electronics and SK hynix as stronger-than-expected earnings from U.S. technology giants revived optimism over artificial intelligence (AI) investment. Foreign investors snapped up more than 7 trillion won ($4.9 billion) in shares. Yet rather than restoring confidence, the dramatic rebound underscored just how disorienting the market has become for retail investors, leaving many to feel less like long-term shareholders than reluctant participants in a high-stakes timing game. The phrase “Roller KOSPI” — a portmanteau of “roller coaster” and “KOSPI” — has become a fixture across online investing forums and social m