The KOSPI index fell 6% due to a shift in sentiment driven by a bearish note on memory from Morgan Stanley analyst Shawn Kim. The note highlights potential oversupply and slowing price increases for NAND and DRAM, alongside concerns that HBM growth will be capped at around 40%. The broader South Korea index is heavily reliant on Samsung and SK Hynix, leaving the market vulnerable to cracks in the memory supply and demand thesis.