Seoul hasn't seen anything quite like this in a long time. By the time BTS takes the stage at Gwanghwamun Square on Saturday, with the storied Gyeongbokgung as a backdrop and an estimated 260,000 fans packed into a stretch of road that normally handles morning commuters, the city will have already spent a week purple. Hotels in central Seoul are booking rooms at five times their usual rate. Subway trains will skip stations closest to the venue. The government has placed the surrounding districts