South Korea proposed taxing unrealized gains on stocks and real estate at a National Assembly forum on Tuesday, triggering what local traders are calling Black Tuesday across the Korean stock market. The proposal would treat paper profits as taxable income even if the underlying asset has never been sold, redefining how wealth is taxed in Asia's fourth-largest economy. Lawmakers from the Democratic Party, the Progressive Party, the Rebuilding Korea Party, and the Social Democratic Party backed the plan, alongside civic groups including the Korean Confederation of Trade Unions and the Federation of Korean Trade Unions. The forum, titled "Exploring the Tax Gap on Asset Income and a Transition to Comprehensive Income Taxation," argued that rising wealth signals a greater capacity to pay regardless of asset sales. The market reaction was immediate and brutal, with major listings plunging across the KOSPI and retail sentiment turning sharply negative as investors feared forced selling to cover annual tax liabilities and potential capital flight.