On the 23rd of October, the KOSPI index in South Korea plummeted due to fears of the widening conflict between the United States, Israel, and Iran, prompting the activation of a sell-side circuit breaker. This marks the 10th instance of a circuit breaker being triggered in the securities market this year, with the sell-side circuit breaker being initiated for the sixth time. As a result, the KOSPI index began trading at 5580.15, down by 3.48% (201.05) compared to the previous Friday's close.

As the trading day progressed, the KOSPI index continued to decline significantly, resulting in the activation of the sell-side circuit breaker at 9:18 AM. This mechanism is triggered when the KOSPI 200 futures index falls more than 5% and remains below that threshold for over a minute, pausing all program sell orders for 5 minutes. This drop in the index affected major conglomerates, with Samsung Electronics noted to have dropped 5.92% and SK Hynix down by 7.35% during the trading session.

Additionally, the KOSDAQ index mirrored this downward trend, starting at 1129.86, which was a 2.73% drop compared to the prior week's close, and fell further to 1106.46, representing a 4.74% decline by 9:50 AM. The exchange rate between the Korean won and the US dollar also faced pressures, starting at 1504.9 won and surpassing 1510 won, marking its highest level in 17 years, reflecting market volatility amidst geopolitical tensions.