Do you know BTS? In case you don’t, or have chosen to wilfully ignore them so far, here’s a quick rundown: they’re a seven-member K-pop group from South Korea, whose music treads the line between multiple musical genres, from EDM to hip-hop. The band is composed of Kim Namjoon (RM), Kim Seokjin (Jin), Min Yoongi (SUGA), Jung Hoseok (J-Hope), Park Jimin (Jimin), Kim Taehyung (V) and Jeon Jungkook (Jungkook). They write, produce and are directly involved in the creative process of all their albums, having won multiple awards, both in their home country and internationally. They were the first K-pop group to win a major American award and to speak at the United Nations. They have more than once been directly tweeted by the president of South Korea. And although they have been actively performing since 2013, this Tuesday marked their first-ever performance in the UK.

These fans sitting around, known as ARMY, are almost as famous as the band itself. Fiercely devoted, they’re able to mobilise themselves en masse and sell out stadiums like no one else – as well as being often misrepresented by media outlets as insane screaming teenage girls with no substance, who “don’t even understand the lyrics”. Because, of course, for some critics young women are not allowed to be passionate about anything without being submitted to ridicule.

Approaching the O2 Arena, on an otherwise quiet sunny day, I see flocks of the band’s fans – like, what looks like a crowd of thousands – gathering around posters of the boys, sitting in circles with bluetooth speakers blasting songs from their discography or queueing up to buy merchandise. In a few hours, they’ll be inside, forming a galaxy that can be seen from the stage by holding up a shining light stick device called the ARMY bomb. The swarm of their glow will symbolise each fan’s place in the stands, extending as far as my eyes can see and flickering, sometimes blue, sometimes multicolour, sometimes purple. Each person in that arena will soon be hanging on to every word spoken, in English and Korean, by the seven young men currently hailed by many as the world’s biggest boyband.

But despite the misguided claims of superficiality, ARMY, standing alongside BTS (as the group always remember to point out), are currently leading a radical self-love movement, propelled by the band’s latest series of albums, Love Yourself: Her, Tear and Answer. Each album openly follows the band’s own collective and individual journey towards self-love, going from a youthful, naive perspective of searching for love in others to coming to love and accept themselves, despite flaws or previous mishaps.

“It’s so sad that some people think that music doesn’t have the same meaning just because it’s in another language – it can be just as beautiful and meaningful”, says Rachel, 15. “They think we’re just fanning over some good-looking guys, and that’s not it. Yes, they are pretty, but that’s not all. They work so, so hard, and they’ve made it so far, and the fact they did that makes you feel like you can do anything you want, too.”

The Love Yourself album series also included a collaborative campaign with UNICEF, LOVE MYSELF, which started in November 2017, raising more than $1 million for the UN agency’s #EndViolence campaign and culminating in RM’s much-blogged, touching speech at the UN. There, he coined a new mantra of acceptance: “Speak yourself”.

“Loving yourself is so important – BTS really made me realise a lot of things”, says Hannah, 17, a BTS fan since 2013. “When I watched RM at the UN – I thought it was funny at the beginning, not going to lie, but it really hit me: he’s right. He was talking about how he didn’t accept some things about himself – so I realised I need to accept where I’m from, because I used to be embarrassed about it – since I used to be bullied for being Somalian and all that. Now I just embrace it. And it’s cool.”

Personally, I stumbled upon my first BTS video three years ago – during the height of my depression, back in my parents’ house, while recovering from a major mental breakdown. The seven members, in their sailor outfits dancing along in perfect sync to a mash-up of “Rollin’” by Limp Bizkit and becoming a human-made machine gun, were the first people to make me feel anything other than the dread and tiredness I’d become so familiar with for the previous two years. Today, sitting here at the concert, at nearly 25 and with my multiple tattoos, I’m wearing a self-made “Goths love Jin” lapel pin and keeping a sign with SUGA’s face on it inside of my bag. I have watched thousands of hours’ worth of BTS videos and interviews and yes, I have them as the background on my phone.