North Korea has yet to allow citizens to openly enjoy the music performed before Kim Jong-un at a concert in Pyongyang this month, arresting and prosecuting teens who dare expose themselves to South Korean “K-pop” without government authorization.

A report in the Japanese newspaper Asahi Shimbun last week, surfacing in English-language media this week, reveals that at least six teenage North Koreans are facing trial for allegedly listening to and dancing to K-pop songs. South Korea’s Chosun Ilbo reports that the trial against the teens occurred weeks before Kim publicly enjoyed K-pop by the group Red Velvet, invited by Pyongyang to perform for the dictator.

According to the Japanese report, four of the teens, whose names are still unavailable, received a year-long sentence at one of North Korea’s notorious labor camps for “plotting against the state” by listening to South Korean music. “The sentence of the other two was not clear. All were sent to a prison camp after the trial,” Chosun notes. The minors were believed to be between 16 and 17 years old.

The newswire service UPI adds that the children not only listened to the songs, which totaled about 50 illegal tracks, but shared them among each other with a USB drive.

Flash drives have become indispensable cultural artifacts in communist countries in the past decade. Like the Cuban paquete, a flash drive published weekly containing the West’s most popular movies, music, and television, North Koreans rely almost exclusively on flash drives for their illegal consumption of media. Despite the possibility of being publicly executed for consuming “imperialist” culture, North Koreans have used videos and DVDs for years to consume media devoid of Kim family propaganda, which constitutes all legal media in the country. Flash drives are significantly easier to use and hide than older technology, however, making it easier to distribute for smugglers.

Perhaps in response to the news of the teens being sentenced spreading around the world, North Korean state newspaper Rodong Sinmun published a column this week warning North Koreans away from “ideological and cultural poisoning.”

“It is important to set up double and treble mosquito nets in all fields of social life and resolutely reject the imperialist idea and culture,” the newspaper warned. “The ideological and cultural poisoning by the imperialists is a hideous reactionary offensive to stamp out the popular masses’ consciousness of independence and undermine their faith in socialism.”

Yet Kim Jong-un himself appeared to let down his guard last week, applauding the K-pop groups Seoul sent to perform in the totalitarian country and taking photographs with groups that North Koreans can be executed for being exposed to. State media reported that Kim and wife Ri Sol-ju were “deeply moved to see our people sincerely acclaiming the performance, deepening the understanding of the popular art of the south side” and published photos of the first couple with the artists. While Kim used the presence of these celebrities for propaganda purposes – and Western outlets were quick to herald it a potential “diplomatic breakthrough” – the artists’ content was heavily regulated. All were forced to sing a political song called “Our Wish Is Reunification” and one artist was forced to perform one of Kim Jong-un’s favorite songs despite the fact that she did not originally perform the song and “didn’t even know” it.

The musicians who performed in the “Spring Comes” concert, as it was officially titled, returned to South Korea with praise for the north. “We were all unbelievably impressed, and it wasn’t until we arrived in Incheon that the magnitude of our experience sank in,” Yoon Sang, the artist leading the troupe, told local media. Musicians said that Kim not only greeted them, but “went up to each table and poured glasses for everyone” at a dinner to welcome them to North Korea.

South Korea organized the concert in gratitude for North Korea sending an art troupe to PyeongChang in February as part of their delegation to the Winter Olympics. South Korean taxpayers were forced to pay for the entirety of North Korea’s presence at the event, yet the government of leftist Moon Jae-in also felt the need to organize a response concert to that event. It represented a significant shift from the policies of his predecessor, Park Geun-hye, whose government used K-pop as an irritant to loudly broadcast across the de-militarized zone (DMZ). In January 2016, to disrupt birthday celebrations for Kim Jong-un, Park ordered the broadcast through loudspeakers of the day’s most current K-pop hits, which Pyongyang denounced as an act of war.

The human rights situation has not improved after Moon took over the south, as recent conviction and labor camp sentence shows. Possessing “illegal” media can result in execution or lifetimes doing brutal hard labor. Particularly sensitive content, like Bibles, can trigger brutal public executions via steamroller or crucifixion. The United Nations suggests that hundreds of thousands of North Koreans may be serving sentences in labor camps.

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