South Korea's hugely popular K-pop and the broader "hallyu" or "Korean Wave" genre of popular culture are experiencing something of a crisis, with domestic sales declining, new bands failing to whip up the same frenzy as their predecessors, and shares in the top K-pop agencies plummeting, suggesting that investors are jittery that the bubble may be about to burst.

The domestic slump coincides with those same performers — BlackPink, BTS, and the irascible Psy, who unleashed "Gangnam Style" on an unsuspecting world back in 2012 — growing in popularity on the international music scene.

The suggestion is that by attempting to broaden its appeal to a global audience — performing in foreign languages, topping the music charts in key markets around the world and being hyped on the chat shows — those bands have forgotten their roots and are in danger of alienating the very people who launched their careers.

Hallyu has, of course, undergone ups and downs in its popularity in the past but has always found a way to reinvent itself or evolve, analysts point out.

The challenge, they suggest, is for the industry to pull off that same trick to keep the home-grown fans coming back, buying the music and attending concerts.

"I would suggest there are absolutely no signs of K-pop declining in popularity abroad and that it is difficult to directly correlate the stock market value of K-pop agencies with the popularity of their bands," said Park Saing-in, an economist at Seoul National University.

"But we can say that stock prices reflect the market's future expectations and while hit bands like BTS and BlackPink are still performing, it is fair to ask where their successors are," Park told DW.

In recent months, new band Baby Monster has failed to make a significant dent in the Melon Top 100, the South Korean ranking for music sales, while ITZY and NMIXX saw their latest releases sink dramatically in their second week, The Korean Times reported earlier this month.

Similarly, sales of the latest mini-album released by girl-group Le Sserafim shrank 20% in the second week of its release.

Uncertainty over the bankability of performers at home has hurt the four biggest management agencies, with stocks in YG Entertainment down by 15% in mid-March from the turn of the year. HYBE was down 19%, while industry giant SM Entertainment fell 22% and JYP Entertainment lost a worrying 33% of its share value in the same period, according to the ChosunIlbo newspaper.

In response to the slump in sales, which account for a major slice of total revenue, agencies are attempting to launch an array of new artistes, with YG Entertainment unveiling the boy-band Treasure, HYBE introducing TWS and Katseye and SM Entertainment pushing NCT Wish.

But it is not at all clear if any of these bands, plus others that are in the pipeline, have what it takes to take over the mantle of super-groups such as BTS.

Other problems have also dogged the industry, with the members of BTS presently carrying out their national service, forcing the band into a year-long hiatus, while other stars have been struck down by scandal.

Karina, a 24-year-old singer with girl-group Aespa, provoked a storm of protest from fans after it was revealed in late February that she was in a relationship with actor Lee Jae-wook.

Agencies encourage their performers not to have boyfriends or girlfriends as that destroys the daydream that they like to promote among fans that these idols are single, and therefore potentially available as a romantic partner, however fanciful that notion might be.

There is a sub-set of fanatical followers who turn up at concerts waving signs that read "my husband" or "my wife" – and revelations that the target of their affections is actually involved in a real relationship is a betrayal that too often leads to anger and accusations on social media.

Whatever the cause of consumers' anguish, that is being reflected in falling popularity at home.

"A lot of hallyu culture reached its peak during the COVID pandemic," said David Tizzard, an assistant professor of education at Seoul Women's University and a columnist for a Korean daily focusing on social affairs. Hallyu is a Chinese term that translates to “Korean Wave” and refers to Korean popular culture, everything from music to movies, food and gaming.

"With people stuck indoors or isolated from others, they turned to the high production values of South Korean music and dramas to get them through it," he said.

"Hallyu is also more than just content, there's a surrounding community and culture which draws people in. They can do more than just watch a drama, they can learn about the actors, read fan fiction, communicate on Twitter and Tik-Tok," he told DW.

When the pandemic ended, some people "moved on," Tizzard said.

"It served a purpose. It was a genuine culture, with visible high points of the movie 'Parasite' at the Oscars and Black Pink and BTS achieving great success, but now that culture has shifted and people are looking for something new."

Tizzard believes that while hallyu culture may not be as wide as it was a couple of years ago, it remains deep and "the fans who engage in it are still as passionate as they always were."

But Park is not convinced that will be enough.

"In the past, South Korea produced a lot of hit television dramas that were hugely popular here and around the world," he pointed out. "But that is no longer the case and the television sector has lost its momentum. The same thing can happen with Korean movies or music," Park added.

"I would say that K-pop appears to be structurally sound at the moment, but the future remains uncertain."