In a city where millions of visitors arrive each year carrying smartphones but not local currency, Busan has quietly removed one of travel's oldest small frustrations. Starting September 21st, the city's buses will accept the mobile payment apps that much of Asia already uses daily — Alipay, WeChat Pay, and others — asking only that a traveler scan a code and ride. It is a modest gesture, but one that speaks to a larger truth: the ease of arrival shapes the memory of a place.