If you’re tired of Korean rapper PSY’s ubiquitous viral hit, “Gangnam Style,” it may be time to pack your bags for Japan. It’s an unsual paradox: Korean pop, a.k.a. K-Pop, is huge in Japan as it is elsewhere in Asia, with artists like Girls’ Generation and TVXQ regularly drawing teenyboppers’ ears. But for a variety of reasons, “Gangnam Style” — which rose to #2 on the U.S. Billboard charts and ha