South Korea’s online secondhand market was once a network of consumer-driven trades, loosely overseen by companies offering little more than secure payments and basic fraud checks. Today, the market is being commercialized with unusual speed, swelling to a projected 43 trillion won ($30.6 billion) this year — nearly double its size in just four years — according to the Korea Internet & Security Agency. Hence the retail platform surge. From peer-to-peer swaps to business-run ventures, all are vyi