Shares of Kakao Pay, which is backed by China's Ant Group, closed at 193,000 won on Wednesday after opening at double the IPO price of 90,000 won. The benchmark KOSPI index finished 1.25% lower. Kakao Pay's opening day performance is the strongest by a company in the main Korean index since Iljin Hysolus Co Ltd's shares gained 160% in September and gives it a market capitalisation of 25.2 trillion won ($21.3 billion). That exceeds KB Financial's 23 trillion won and lags only the 28.2 trillion won of affiliate Kakao Bank - which listed in August - among financial companies. "The red-hot IPO demand may have peaked sometime earlier but the market is still very friendly to platform business IPOs. Kakao Pay's solid debut is proof and dispels concerns about regulatory issues," said Sung Jong-hwa, analyst at eBest Investment & Securities.