Hope, Jimin, V and Jung Kook — recently completed South Korea’s mandatory military service, and hope to reclaim their status as one of the world’s biggest pop acts.

The concert in Seoul’s historic center was a grand homecoming for a pivotal force of South Korean soft power. RM, the group’s leader, performed through an ankle injury.

The K-pop superstar will have to limit movement during Saturday’s global livestream from Seoul, which marks BTS’ first ...