Ahead of Saturday's special live performance marking K-pop giant BTS' long-awaited return, Seoul transformed into a sprawling open-air festival overnight, as fans poured into the heart of the city, turning weekday streets into scenes of celebration. The stone walls of the 600-year-old Sungnyemun gate, a key national treasure of South Korea, lit up with alternating white and red logos of BTS and its new album, "Arirang." Accompanied by a deep rumbling sound, the silhouettes of the seven members a