Do you know BTS? In case you don’t, or have chosen to willfully 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.

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 symbolize each fan’s place in the stands, extending as far as my eyes can see and flickering, sometimes blue, sometimes multicolor, 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.