Upgrades by major financial institutions like Citigroup generally lead to positive investor sentiment and can cause a short-term increase in stock price. The upgrade from Neutral to Buy suggests a strong belief in the company's potential for growth, and the increase in price target further supports this optimistic outlook. Given Citigroup's influence in the market, this upgrade is likely to attract attention from investors and could lead to an increase in demand for Sea's stock, pushing the price up in the short term.