It was five o’clock on a Sunday in May, two hours before showtime, but already thousands of K-pop fans had flooded the concrete playa outside the Honda Center, a large arena in Anaheim, California. Tonight’s performers were among the biggest pop groups in South Korea—shinee, f(x), Super Junior, EXO, TVXQ!, and Girls’ Generation. In the United States, Korean pop music exists almost exclusively on YouTube, in videos like “Gangnam Style,” by Park Jae-sang, the rapper known as PSY, which recently went viral. The Honda Center show was a rare chance for K-pop fans to see the “idols,” as the performers are called, in the flesh.