The return of BTS on Friday comes at a moment when K-pop’s global reach is firmly established — and still growing. On Saturday, the seven-member group will reunite onstage for the first time in nearly four years. The concert, set in Gwanghwamun Square in central Seoul, is expected to draw about 260,000 fans from around the world, a testament to the group’s enduring pull even after years away. BTS’ military hiatus did little to slow K-pop’s momentum. Acts like Stray Kids and NewJeans have continu