Last October, the four-piece girl group 2NE1 debuted in Japan with six live shows in front of 70,000 fans—the latest product of a South Korean music machine that has already surged past the point of being just another East Asian fad. While “K-pop” has gained popularity as the catch-all term for a host of glossy boy and girl bands, 2NE1, with its signature tune, “Ugly,” represents K-hop, a budding movement that backs up its slick pop sheen with true R&B talent.