A hedge fund that started this year is producing double-digit returns in South Korea even as the stock market slumps. Billionfold Asset Management Inc. has returned about 15 percent since January mainly through a long-short strategy focused on South Korean equities, Chief Executive Officer Hyungjin An said in an interview in Seoul. The Kospi index has fallen 9.2 percent this year. The firm has attracted 440 billion won ($389 million) to its four funds, mostly from retail investors, An said. Three of Billionfold’s seven fund managers have spent some time as day traders, one for as long as 10 years.