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"Destroy the stage." That's the advice RM, the composed leader of one of the biggest pop acts in the world — BTS, of course — gave to their young, wide-eyed labelmates ahead of their first U.S. showcase tour a few months ago. "It's all about your attitude towards the performance," dancer and rapper J-Hope added. "Because fans know if you're putting your heart into it."

Watching the five members of Tomorrow X Together confidently take the stage at the PlayStation Theater in May, in the heart of New York City's Times Square, it was clear that they were listening closely to their seniors. They performed their entire discography — all five songs — and communicated entirely in English in front of a sold-out crowd of over 2,000 fans. Not bad for a group that's only a few months old. Though, Tomorrow X Together, pronounced "Tomorrow by Together," aren't your average rookies.

For an emerging Korean group, a U.S. tour is a milestone years in the making, but the steady demand for K-pop abroad has reached a fever pitch in recent years, making the Western market more accessible than ever. But for Tomorrow X Together, whose March debut EP The Dream Chapter: Star landed on the Billboard 200 and topped the World Albums chart, selling out their first U.S. showcase wasn't just a testament to the international fanbase they've accumulated in such a short period of time; it was a chance to prove themselves as artists and performers — as more than BTS's "little brothers."

Needless to say, the pressure was on, but they didn't let it show.

"We learned that we can perform in front of a lot of fans," youngest member Huening Kai told MTV News of their first showcase in New York. "At first we were so nervous, but now I think it was really fun."

But did they destroy the stage? "Of course!" said Taehyun, the group's most quietly self-assured member despite his age. Leader Soobin takes a more practical, measured approached: "I think we did our best," he said. "We are so thankful for BTS's advice."

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From left to right: Taehyun, Beomgyu, Huening Kai, Yeonjun, and Soobin

Standing in front of the five members — Soobin (18), Yeonjun (19), Beomgyu (18), Taehyun (17), and Huening Kai (16) — in an executive suite of a Manhattan hotel in July, it's easy to see how this group of teens has captured the hearts of Korean and international fans alike. They are attentive and jovial, even after a 14-hour flight from Seoul. "I watched Iron Man and Iron Man 2 on the plane," Beomgyu said excitedly in English. He's currently in the midst of an Iron Man phase, and in case you're wondering: No, he hasn't seen Avengers: Endgame; yes, he knows what happens to Iron Man. "I didn't watch Endgame either, but they spoiled it," oldest member Yeonjun added, pointing to Taehyun, Huening Kai, and Soobin, who are all sporting knowing grins. "They spoil everything."

Spoilers, like disagreements, are unavoidable when five individuals spend the majority of their waking hours together, training and rehearsing. Like BTS before them, TXT (as they're commonly referred to) even share one bedroom; the older members on the bottom bunk beds, the younger three on the top. "Hanging out with them is always fun," Taehyun said with a wide smile. "We get very noisy," Yeonjun added softly.

But he's also quick to point out that it isn't all fun and games and Marvel movies; they "talk about hard stuff" too. "We have different traits, and I think that makes us more special," he said. "Everyone has different personalities and [ways of] thinking, but when there's a problem we solve it as one team, five to one. We understand each other."

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As such, weekly team meetings and alone time pursuing individual passions are a must. For Taehyun and Beomgyu, that means long walks at night, separately and together. "I feel most creative when I walk alone at night," Beomgyu said. "I think about lyrics and my performance." Ever the perfectionist, the dancer and singer is currently learning music production in the hopes of contributing to future albums — not unlike his idols, BTS.

"I feel a lot of emotions at night," added Taehyun. "It's so busy during the day." It's during these quieter moments that he listens to music and concentrates on his own performance. "I'm always singing," he said, adding that he's been listening to a lot of Kehlani's music lately.

Soobin, too, finds comfort in the reassuring voices of his idols: Beyoncé, Adele, and, of course, his undisputed favorite, Bebe Rexha. "These days I'm interested in singing, so when I listen to music I sing along," he said. Surprisingly, his most recent interest has nothing to do with music — or Rexha — at all: "These days I drink sparkling water every day." But he's quick to add, "No flavors."

For Yeonjun, the group's main dancer and anointed rapper, his creative outlet is through movement. "I'm most creative when I dance because I can do whatever I want," he said. "I can express my feelings and emotions through dance." And he will, regardless of place or time. "I will dance any time there is good music." (His members enthusiastically agree.) That need to constantly keep moving also extends to his free time away from the fluorescent lights of the practice room.

"Do you know wakeboarding?" he asked. "I started wakeboarding, and I really got obsessed. I love the speed."

And then there's Huening Kai, a multi-instrumentalist and singer whose talent continues to surprise fans and his members. "He's a good painter," Taehyun said of the group's tall maknae (youngest member). "I like to draw cute animals or characters, like Pokémon — and also our members," Huening Kai said sweetly. (His favorite Pokémon are Eevee and Pikachu, confirming his affinity for cute things.)

Tomorrow X Together's youthful demeanor permeates throughout their music as well. Their debut single "Crown" found the pop quintet pondering the pangs of adolescence over an energetic synth-pop beat; the crowns they sprout are symbolic of the physical, emotional, and mental changes that all young people endure as they grow up. "Wanna run away," they sing. "Wanna disappear / Far away / Who am I / I don't know who I am."

Like their music suggests, they find strength in each other and their shared coming-of-age experiences — like how to appreciate the things that once felt like burdens. "When I started singing, I thought my voice was awful," Taehyun, who was a Big Hit Entertainment trainee for three years, said. "But now it's OK," he added, modestly.

"I used to be more of an introvert, but I think it became my strength," Huening Kai added, explaining how being with his members helped him come out of his own shell. "I'm not like that as much as before."

When they opened the first night of KCON New York, the annual two-day Korean pop culture convention and concert, at the famed Madison Square Garden on July 6, there wasn't a trace of insecurity or doubt. They showed boundless energy and poise, looking even more polished than they did two months ago. And when thousands of attendees started barking at them — the unofficial fan chant of their second single, "Cat & Dog" — they didn't look surprised; they looked exhilarated, like five stars who felt truly at home on the stage.

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Tomorrow X Together make their KCON debut inside New York City's Madison Square Garden

With a successful U.S. showcase and an electrifying performance at their first KCON under their belts, Tomorrow X Together are already looking ahead to their future. "I think we all share the same goal," Beomgyu said, his soft tone becoming slightly more determined. "Our goal is to get nominated for a Best New Artist award by becoming a super rookie." He ends with a common Korean phrase of encouragement: "Hwaiting!" His members join the cheer, raising their fists with purpose.

Meanwhile, Yeonjun has a short-term, albeit far less attainable, goal in mind first. "I want to watch the new Spider-Man, but we don't have enough time." Such is the life of Korea's most buzzed-about rookies.

Besides, it's only a matter of time before his members spoil it for him anyway.