In South Korea’s sputtering economy, where stocks have been falling since the start of last year, one way to generate returns has been in the risky world of startup investment. One hedge fund firm, AlpenRoute Asset Management, has gained 81% in its flagship fund since inception in July 2016, by investing in unlisted companies such as the firm behind K-pop boy band BTS. AlpenRoute, which oversees about 1 trillion won ($836 million), benefited as revenue at Big Hit Entertainment Co. more than doubled last year on the success of BTS.