Kicking off their global tour in the South Korean city of Incheon, the five members of K-pop boy band Cortis saunter onto stage in casual, streetwear-inspired outfits, exuding an effortlessly cool vibe.

“Put your phone down,” one of the members bellows. Piercing screams erupt. A sea of illuminated screens flickers back.

“I told you, put your phone down,” he repeats, louder this time.

Some fans do just that, but the packed stadium vibrates harder with cheers as thousands of phones stay in the air.

It’s hard to say how serious this theatrical command is.

“Put your phone down” is also the name of Cortis’s ongoing concert tour, which started in Incheon on 18 July and will head to cities like New York and Los Angeles before returning to Seoul later this month.

The refrain reflects a message the band has long pushed: that fans should stop watching concerts through six-inch screens and engage with their performances in real life.

It’s drawn mixed reactions from their fandom: fan-filmed content is a valuable social currency in K-pop.

Park Ji-yeon, for one, could not bring herself to stop recording Cortis’s performances. The 22-year-old had specially rented a new, top-tier smartphone for both days of the Cortis concert just so she could film in the highest quality.

“I was standing right at the front, and I couldn’t bring myself to put my phone down because I don’t know if I’ll ever get this opportunity again,” she tells the BBC.

“I usually film concerts because I know a lot of those memories will fade as soon as I leave the venue.”

While fans like Park continued to film, some heeded the band’s call. Kim Ga-eun, 25, who was seated in the amphitheatre-style venue, saw it all.

“People in the back of the standing section were having a great time dancing together. I thought that really reflected the intention behind the concert,” she says.

Cortis has had a whirlwind year since debuting last year under record label BigHit Music – part of the company that created pop sensation BTS. Most of its members are teenagers. The oldest of the group, James, is just 20 years old.

Their music videos have each amassed millions of views. Over the weekend they performed at Lollapalooza, the famed music festival in Chicago.

The band’s name, Cortis, is derived from the phrase “colour outside the lines”, which according to their record label is meant to encapsulate the band’s free spirit and refusal to conform to societal rules – which, in this case, appears to include telling fans to resist the temptation of the phone camera.

They join a prominent wave of artists around the world who have been advocating the same.

Singers like Phoebe Bridgers and Alicia Keys have required their concert attendees to use lock pouches – sealed bags that allow people to hold on to their phones without being able to access them.

Few have gone as far as Welsh rock group Suede, whose frontman Brett Anderson leapt over a barricade during a 2023 performance in Singapore to grab at fans’ phones.

Billie Eilish, who has defended filming as a way for fans to relive precious memories after a show, gently cooed to her front row audience during a performance in Amsterdam: “Put your phone down, I’m right here.”

Even BTS, K-pop’s golden boys, have made similar requests. “Stop looking at your phone screen. Just look at me,” BTS member Jungkook teased the audience at one concert.

“From the artists’ perspective, interacting with fans is a really important part of performing, so I think they want people to focus more on that than on their phones,” Park says of Cortis’s anti-mobile rallying cry.

After all, fancams – zoomed-in videos focusing on a single celebrity – are a prized currency in K-pop communities. Once shared online, people meticulously study the choreography in them and delight in catching subtle movements and expressions by their favourite band members. These clips live on as fodder for collective swooning and fan-made montages.

And this is why Cortis’s incessant calls to for people to put their phones down have rubbed some the wrong way – in a fan culture that’s obsessed with capturing every moment. After the first day of their concert, disgruntled comments emerged online among fans.

“I spent over one million won ($700; £520) attending both days,” Park says. “I think a lot of fans spent similar amounts of money, so constantly hearing them asking us to put our phones down made some fans even more frustrated.”

These murmurs appear to have reached Cortis, who fans say dialled down their message on the second day of the concert.

“On the first day, the message felt more like, ‘Let’s put our phones down and have fun together.’ On the second day, it changed slightly to, ‘We understand why you want to film, so let’s just make sure we enjoy ourselves together,'” Kim recalls.

“They said filming was okay, but they wanted us to enjoy the concert together, and that ‘Put Your Phone Down’ was more of a mindset.”