RM and J-Hope of BTS meet Billie Eilish during her concert in South Korea

Billie Eilish just had a concert in Seoul, South Korea for the first time in four years, and two members of BTS were sure to attend.

Rappers RM and J-Hope were spotted by fans having the time of their life at the concert on Monday evening, with videos showing them dancing to "You Should See Me In A Crown" and cheering during "Ocean Eyes."

Not only that — they also got to meet Billie and her brother-slash-producer Finneas backstage.

RM posted a group photo on Instagram, captioning it "bad guys," a reference to one of Billie's hit songs.

Billie reported the photo on her Instagram Stories.

20-year-old superstar Billie Eilish is currently on tour for her second studio album "Happier Than Ever." Her award-winning debut album "When We All Fall Asleep, Where Do We Go" was released in 2019. —JCB, GMA News