In December 2005, a trader at Mizuho Securities made a devastating error by entering an order to sell 610,000 shares of J-Com Co. at ¥1 each instead of one share at ¥610,000. This typo resulted in an immediate loss of $225 million, marking it as one of the most significant mistakes in financial history. The order was executed on the Tokyo Stock Exchange almost instantly, allowing buyers to purchase shares at a fraction of their actual value. Despite Mizuho's attempts to cancel the order, it was too late, and the transaction proceeded, leading to a flurry of market activity that capitalized on the price difference. The incident underscored the vulnerabilities in trading systems and prompted discussions about financial risk management in high-speed markets. Its simplicity—stemming from a single error—has made it a lasting example of the potential consequences of trading mistakes.