To call the musicians known as BTS "superstars" seems an understatement. Their arena shows in Chicago, New York and Los Angeles have all sold out; they have more than 19 million Twitter followers; they've topped the Billboard record charts; and Time just put them on its Most Influential People List.

And yet these phenoms may not be familiar. So, meet BTS (which stands for "Beyond the Scene"). They're pop stars from South Korea, kings of a world known as "Korean pop" – K-Pop. And it's an industry worth $5 billion.

The K-Pop band BTS, a music phenomenon that has stretched far beyond South Korea. CBS News

Remember the Backstreet Boys? That boy band provided the soundtrack for much of the '90s in America, along with groups like NSYNC. About the same time, thousands of miles away, K-Pop was helping to put Seoul on the pop music map.

But now, BTS, whose first album debuted in 2013, has moved beyond the scene in Seoul, and is coming ashore in America, big time. That their upcoming U.S. tour is one of the hottest tickets on Earth is even more remarkable considering most of their songs are not in English.

To watch BTS perform "Boy With Luv (feat. Halsey)" click on the video player below:

Its members, between the ages of 21 and 26, go by their nicknames: Jung Kook, Jin, Jimin, Suga, V, J-Hope, and RM.

Correspondent Seth Doane, who caught up with the band at their studio in Seoul, asked, "How did you learn English?"

"I love hip hop," said RM, who was signed first, and as the fluent English-speaker, often takes top billing. "I love the pop music. And I love the 'Friends.' Yeah, the TV show. My mom bought me the full series. I watched it, like, several times. I just want to speak and to listen and to understand musicians in America. I just want to say, 'Thank you, Mom!'"

Not long ago, the boys of BTS idolized the stars they mixed with at this year's Grammys. RM said, "I suddenly think, like, Am I really here?"

They became the first Korean pop band to present at the Grammys, after their fans launched a social-media campaign. At the awards ceremony RM said, "Thanks to all our fans for making this dream come true. And we'll be back!"

Doane asked, "What'll it take 'to be back'?"

"We have to practice the same choreography, like, again and again several hours every day," RM replied. "We have to keep the promise."

Did someone say "choreography"? Everything BTS does is meticulously choreographed … including, say, their arrival to rehearsal, on this day in five separate cars. We cannot tell you just where they were rehearsing; over-enthusiastic fans pose a constant security risk.

Doane asked, "Can you describe that enthusiasm?"

"I'm amazed by it," J-Hope said, "to receive all this love."

Jimin said, "I think we were able to quickly engage with our fans by being sincere with our feelings. We try to share our emotions with our fans."

Members of the K-pop sensation BTS. CBS News

And those fans feel BTS truly understands and supports them. One fan, Alice Meune, told Doane, "They're not just a band. They are a support. They are inspiring, and they really helped me in the past."

In what ways? "About loving myself."

Whenever BTS begins a performance, Jung Kook told us, "I take out my earpieces and listen to the shouting and screaming. It fills me with energy."

And BTS fans (they call themselves ARMY) aren't just enthusiastic; they're enthusiastic consumers.

Which is why the guys adorn the sides of soda cans, and even teamed up with artists who designed their stuffed-animal alter-egos.

K-Pop is such a phenomenon that in the Seoul subway system fans will even pay to put up giant signs celebrating their favorite K-Pop star's birthday. These super-sized posters are as close as many will get.

A BTS fan gets up close with a subway poster featuring J-Hope. CBS News

This is where we should mention that the guys have a new album out, and that "Sunday Morning" was the first American network television program granted this sort of behind-the-scenes access.

And in case you're wondering what's up with the face masks, the constant air pollution over much of South Korea makes the masks a lot more than a fashion statement.

The boys of BTS consider themselves family. They've trained, composed music and grown up together – and yes, they all live in the same house.

"At first, we were like, 'Why do we have to live together?'" Suga explained. "But at some point we realized that this is really precious. And we've become really thankful."

V told Doane, "I think these are the people who know me the best. We know each other better or more than our families know us."

But they can retreat to their own private spaces. RM showed Doane his studio, and the toys that he loves.

"You spend time in here composing, thinking of the next song?" asked Doane.

"Yes, and writing lyrics," he said. "And sometimes shopping, you know, E-bay."

"So, it's not work all the time?"

"No, no, no!" he laughed.

How long all this will last is anyone's guess. But there is this: Military service is mandatory in South Korea, and there is only so long the band's members can delay serving. "As a Korean, it's natural," Jin said. "And, someday, when duty calls we'll be ready to respond and do our best."

Doane asked, "Do you worry about breaking off, separating, going different ways?"

"I don't want to think about it at this point," said Jung Kook. "We have something really good going."

RM added, "That's the answer. We just enjoy the ride, live in the moment, and that's all we can do."

Now that ride is taking them back to America, where awaiting them – among other things – is a line of BTS dolls, from Mattel, the makers of Barbie. Twenty dollars a (K-)pop.

BTS dolls. Mattel



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Story produced by Jay Kernis.