BTS is back - but the K-pop superstars are returning to a changed industry

"I missed them so much," says Stephanie Prado, a die-hard BTS fan who has been desperately waiting for the group to reunite after a two-and-a-half-year hiatus.

Her love for the boy band inspired her to move from Brazil to South Korea - so it was no surprise that she turned up last Friday for "BTS Festa", a big party held every year near Seoul on the group's anniversary.

The time she has spent waiting has moved "both slowly and really quickly", Stephanie says, waving an ARMY bomb, the official lightstick used by BTS fans, who call themselves the ARMY.

Behind her is a huge sculpture of the lightstick, a must-have in the K-pop world.

This year's event is special because a reunion is finally around the corner. The countdown peaked last week, when four of the seven members, RM, V, Jimin and Jung Kook, completed their military service. And the wait ends on Saturday when the last of them, Suga, is discharged.

"I hope they rest now," Stephanie says, before adding, "but of course I also want albums, concerts, everything".

The 18 months in the military that are mandatory for all South Korean men forced the world's most successful boy band in recent years to hit pause in 2022. Now they are returning, some say, to a K-pop industry that is quite different to the one they knew: faced with stalled album sales, shaken by scandals and increasingly scrutinised over the excessive pressure it puts on stars.

The absence of a leading band, industry watchers say, was deeply felt.

"Without BTS, a core pillar was missing," says Kim Young-dae, music critic and author of BTS: The Review.

"There have been concerns recently that K-pop is losing momentum. True or not, BTS could change that perception."

There are no plans yet for all seven members to appear together, but that didn't stop the ARMY from gathering early on a humid morning in Goyang.

The long, restless queue stretched to the subway station an hour before the gates for the BTS Festa opened. The snippets of English, Chinese, Japanese and Spanish alongside Korean threw off a local walking past who asked, "Why are there so many foreigners here?"

Inside were more queues - some people were hopping with excitement and others were sobbing after entering the "voice zone", a phone booth where you could listen to BTS members' messages. About half of the fans the BBC spoke to teared up talking about how much they missed BTS.

"It felt like the 18 months lasted forever," said Vuyo Matiwane, a South African who had been visiting BTS-themed venues in Seoul, like their favourite restaurant. "I was crying at every location - it was so emotional."

And then she watched the livestream of them being discharged, which was "overwhelming".

Being surrounded by all things BTS made a trip halfway across the world worth it, says Fara Ala, who travelled from the Netherlands: "Breathing the same air, drinking the same water, eating the same food as BTS - that's enough for ARMY. If you ask other ARMY, they'd say the same."

South Korean military service is a major test for male celebrities, many of whom have to enlist at the peak of their success. In the past, it has proved fatal for some careers.

BTS is believed to have staggered it so that all seven members were missing from action for no more than six months. J-Hope, who was discharged last October, has since wrapped up a solo world tour. But the so-called curse can be hard to break.

For one, the loyalty of fans could wane as new groups debut almost every week, competing for their attention. Returning idols also face a tough transition because a military stint and a touch of maturity could dampen the essence of K-pop appeal: youthful energy.

But if anyone can break the curse, it's BTS, Mr Kim says.

Each of them announced solo projects in the past two and half years, he explains, without hurting their popularity as a group: "It feels like their military hiatus passed by naturally. Their return feels smooth."

Still, the industry beyond the ARMY can pose a challenge.

While BTS was on a break, the other K-pop sensation, Blackpink, has not dropped an album since September 2022, opting instead for solo releases. These were the leaders of K-pop's third generation.

But they have been succeeded by fourth and fifth generations that have brought fresh style to the genre. The newer acts - which debuted after 2018 - lack a standout name like BTS because K-pop has become more diverse than ever. The result is a range of very popular and experimental groups.

"Most people my age like fourth generation idols these days," says a 13-year-old fan of girl group IVE.

"Some still like third generation groups, but for teens, BTS kind of feels like they belong to an older generation. A lot of new idols debuted while BTS was away, and they have become popular."

But the biggest challenge to BTS' superstar status is what some see as a slowdown in K-pop.

Revenue from concerts remains strong, but album sales - a key market metric - have been declining since a peak in 2023. The slump coincides with when BTS and Blackpink were not releasing albums.

South Korean pop culture critic Park Hee Ah agrees that K-pop went through "some difficult times" while BTS was away.

There have also been several controversies, such as the headline-making dispute between hit girl group NewJeans and their agency, allegations of mistreatment by all-powerful agencies and harassment of stars by fans and trolls.

"Album sales started to drop, and some problems - like questions about companies doing the right thing - came up," Ms Park said. Because of all of this, she adds, we did see more "deeper problems in the K-pop industry".

That's also why so many are looking forward to BTS' return, hoping it will bring renewed energy - and maybe even a path forward for the industry.

"Their return will help people focus on Korea's music scene again," Ms Park says, adding that a BTS reunion is great not just for their fans but also for Korean soft power.

All eyes are now on the band's next song.

"I will quickly make an album and return to the stage," RM, the group's leader, said on the day he was discharged.

But a new group album may not come until early next year because J-Hope still has domestic concerts scheduled, and Jin is set to hold concerts for fans across the world over the next few months. It's also possible Suga, who landed in controversy after he was caught drunk-driving a scooter last year, may want to lie low for a little while.

For millions of fans like Stephanie though, simply knowing BTS is back together is enough - for now.

"It'll feel like nothing ever changed. The kings are back."