“Is the love to you by your fans not enough? Why did you choose to betray the fans? Please apologise directly. Otherwise, you will see a decrease in album sales and empty concert seats.”

This was the message driven, on an electronic sign, to the headquarters of SM Entertainment in Seoul, South Korea, according to media reports in the country.

Why? The company formed and manages K-pop band Aespa, of which singer Karina is a member; this was the reaction after it emerged she was in a relationship with actor Lee Jae-wook.

Karina quickly published an image of a handwritten note, apologising for disappointing her fans and promising to “heal the wounds”.

Now, just a couple of weeks later, their break-up has been announced. SM Entertainment confirmed the split to Sky News, but did not comment.

Only a few days before this, South Korean actors Han So-hee and Ryu Jun-yeol reportedly announced their separation, just two weeks after publicly acknowledging their relationship.

Of course, celebrity couples break up all the time, and there are music stars from all over the world whose fans can sometimes take things too far when it comes to their love for their idols.

In 2022, Harry Styles and his then girlfriend Olivia Wilde addressed “toxic negativity” directed at her from a small corner of his fanbase. Last year, Taylor Swift reportedly told the crowd at a show in Minneapolis that fans should not “feel the need to defend me on the internet against someone you think I might have written a song about 14 million years ago”.

But while diehard fans can overreact to relationships and splits, in the K-pop world there is also controversy around the messaging put out by management, with agencies reportedly keen to promote their stars, known as idols, as romantically obtainable.

UK K-pop expert Felicity Davies, from SOAS (School of Oriental and African Studies) University of London, is writing a PhD on the industry and its fandoms, and says it is common to hear of strict dating rules and even dating bans within the industry.

She points out examples of how going public with romantic relationships has worked out for some K-pop idols, such as Blackpink star Jisoo and actor Ahn Bo-hyun – reports they were dating emerged in August last year and the split was announced in October – and fellow Blackpink star Jennie and Exo boyband member Kai. His bandmate, Chen, is married with children.

“However, there does certainly seem to be a lot of pressure on artists to remain as clean cut as possible and to not be caught doing anything that could potentially be seen as ‘scandalous’, and often dating has appeared to come under this ‘scandalous’ label,” she says. But there isn’t “one unified way all K-pop agencies seem to approach this”, she adds.

In 2018, the stock of record label Cube Entertainment dropped several points after two of their artists, Hyuna and E’Dawn, began dating. It led to them both being removed from the agency’s roster.

“They soon signed with P Nation, an agency that takes no issue with dating, and they were able to continue with their careers in the music industry for multiple years while publicly together, even releasing duets at times,” Felicity says. “Different agencies have different approaches.”

The origins of modern K-pop date back to the 1990s, but perhaps the biggest turning point for Western audiences came from the unlikely source of South Korean rapper Psy and his single Gangnam Style.

Released in July 2012, by December of that year it had become the first YouTube video to reach one billion views.

Since then, the genre has evolved and become a multibillion-dollar industry, making worldwide stars of boybands such as BTS and girl groups like Blackpink. In 2019, BTS became the first ever Korean act to score a UK number one album, with Map Of The Soul: Persona – which also became their third Billboard number one album in less than a year in the US. They also sold out Wembley in 90 minutes.

BTS announced a hiatus in 2022, with several members now undertaking mandatory military duties, but there are still plenty of acts filling charts around the world, including Stray Kids, Fifty Fifty and NewJeans.

Last year, 35 different K-pop albums entered the Billboard 200, and five topped the chart.

The fandoms are huge – but not all fans have such extreme reactions to romantic relationships.

Despite the backlash she has faced for her relationship with Lee Jae-wook, many of Karina’s followers have been supportive.

In fact, looking at the response to her Instagram post, which has received more than 2.6 million likes, the vast majority have called out her need to apologise. “Apologise for loving someone?” one wrote. “You don’t need to do this, you deserve to be happy.”

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Felicity says that while there are still restrictions, K-pop stars have more freedom now than they did 15 years ago.

“I do also think that if the ‘anti-dating’ fans continue to become more widely recognised as the inappropriate exception, and the less bothered ones the expected norm, industry restrictions towards dating will continue to ease even more,” she says. “Hopefully to the point where idols will be able to date freely without fear of such negative reactions.”

But she adds: “However, as the situation with Karina and Lee Jae-wook shows, we’re not quite there yet.”