Japan's relationships with China and South Korea have long been strained, with many grievances stemming from World War II. But entertainers from all three countries have long been welcomed across Asia. Japan, boasting the world's second largest music industry behind the United State's, historically has held the most sway in the region. Japanese media has even had several boom periods in Korea. And last decade, Korean entertainers like BoA and TVXQ built big followings throughout Asia. Chinese performers also made their mark, with pop stars from the 1970s (Terese Teng) to the '00s (Faye Wong) becoming famous, even in the hard-to-break-through Japanese market.

The balance of influence changed, though, with the "Hallyu Wave," a term referring to the Korean pop-culture boom that gained steam in the mid 2000s. Spurred by the continental success of the aforementioned singers and of various Korean drama programs, "K-Pop" became a juggernaut in Asia , with groups like Girls' Generation and KARA dominating charts across the continent from summer 2010 to 2012. Popular Korean boy band Super Junior even created Super Junior-M, a Mandarin-speaking outfit made for the Chinese market and that has seen multiple No. 1 hits in a and Taiwan.

The deluge of Korean media, particularly in Japan, wasn't met with completely open arms. Japanese actor Sousuke Takaoka was fired from his promotion agency in July 2011 after taking to Twitter to criticize the Fuji TV network for airing so many Korean dramas. The next month, a series of nationalist-tinged protests were held outside of Fuji TV, with thousands of people showing up to rally against the Korean wave. These anti-K-Pop sentiments carried over to the web, where users of message boards like the often-nationalistic 2chan further bashed Korean entertainment crossing over into Japan.

In 2012, though, Japan's relations with China and Korea grew even more strained. A long-running dispute flared up in the Sea of Japan over the uninhabited Senkaku Islands (or Diayou in Chinese), which are claimed by both Japan and China, when China encroached on the territory and then-Tokyo Governor Shintaro Ishihara proclaimed he would buy the islands. The situation became so intense that violent anti-Japan protests erupted across China. A similar squabble broke out between Japan and Korea when as then-South-Korean President Lee Myung-Bak made a controversial visit to the disputed Liancourt Rocks.

In Japan, the reaction to Myung-Bak's move was less in the realm of politics than it was in the realm of pop. Korean actor Song Il-guk had planned to make a trip to Japan last August, but after taking part in a swimming relay to the disputed territory, Japan's vice foreign minister said it would be difficult for the drama star to come to the country, and the network showing his drama cancelled the program. Political statements K-Pop stars made years before came under new scrutiny, with the group Girls' Generation getting grilled by Japanese fans and media for pro-Korea comments made at a concert three years earlier regarding the disputed islands. Staying silent also prompted rebukes, as popular six-piece KARA was slammed by Korean fans when its members remained mute about the dispute. Even though "Gangnam Style" didn't take off in Japan like it did elsewhere, that didn't stop netizens and CYZO from speculating that Psy's success was the result of Korean YouTube hacking.