first listen, "RBB (Really Bad Boy)" is a song that really shouldn't work. It's a cacophony of sounds, rhythms, shrill ad-libs, complex harmonies, and a whole lot of brass. For a lead single, it's unapologetically bold and loud — the kind of song that beats you into submission with a powerful "oh my God" straight to your temporal lobes — but that's what makes it so unabashedly Red Velvet.

Since making their debut in 2014, the Korean quintet has been serving up their distinct flavors with powerhouse vocals and boundless personality from members Irene, Seulgi, Wendy, Joy, and Yeri (who officially joined the group in 2015). When it comes to K-pop, it all starts with a concept, and Red Velvet's artistic DNA is written into their name: Red signals their vivid pop aesthetic with quirky songs like "Power Up" and "Peek-a-Boo," while Velvet speaks to their moodier, more sensual R&B side, as demonstrated on this year's acclaimed single, "Bad Boy" (a.k.a. Billboard's No. 1 K-pop song of 2018).

It's this duality — the constant push and pull between fierce and playful, sweet and soulful — that make Red Velvet such a mellifluous treat, especially in a musical landscape that likes to put female artists in boxes. In K-pop, girl groups are often one or the other: sweet (TWICE) or sexy (MAMAMOO), girls who produce perfect pop confections (Girls' Generation) or girls with attitude (2NE1). But Red Velvet prove that one concept can't contain the artistry and multitudes that girl groups really have to offer. With "RBB," the titular lead single off their latest EP, Red Velvet aren't playing by anyone's rules, and that's the point. "We just wanted to show people our confidence," vocalist Wendy (who was born in Korea but spent her formative years in Canada) told MTV News about the release.

Though intended as a thematic follow-up to "Bad Boy," the two songs couldn't sound any more different. On "Bad Boy," the women embraced their velvet personas with smooth vocals and a lush girl crush aesthetic; "RBB" is campier by nature but sonically more complex, with tight vocal harmonies and erratic ad-libs from Wendy, Irene, and Seulgi.

"'Bad Boy' was loved by so many people, so that's why we came back with 'Really Bad Boy," Wendy said, describing the song as another entry in the "Bad Boy" series. "They're both talking about bad boys but in different ways. This song is about the girl saying, 'You can go ahead and seduce me, but you really can't because I'm going to seduce you.' So the girl has all the power."

RBB — the album and the song — has confidence in spades. Each of the five tracks (or six, if you count the English version of "Really Bad Boy") find the women of Red Velvet in full control; they know exactly what they want on the assertive, bass-heavy bop "Sassy Me," and give in to temptation on "Taste," a melodic hip-hop song with a '90s groove.

Red Velvet members from left to right: Yeri, Wendy, Irene, Joy, and Seulgi

For Red Velvet, the message of RBB was clear: "You can be whoever you want." And each track is meant to empower and embolden the listener. "There's confidence in every song," Wendy said. "We tried to show people that you can be whoever you want if you just have confidence." As for which songs bring out their own confidence, Red Velvet unanimously pick "Sassy Me" as an album highlight.

"I like all the songs," Wendy clarified, before jokingly adding, "because they're our songs."

That self-assertiveness and swagger also extended to the recording process. "You have to have confidence while recording because whoever is listening to it has to feel it, too," Wendy said. "So we tried our best to have a lot of confidence." Though, it wasn't always easy, especially when it came time to sing in English.

In December, Red Velvet released an entirely English version of "RBB" — complete with its own music video — for their fans all over the world. "We performed an English version of 'Bad Boy' at KCON, just the first verse, and lots of people loved it," Wendy said, noting how when it came time to prepare for their next comeback, or new release, the group wanted to "give this love back" with an English track. "We know that we're getting lots of love from people in the U.S.," she added.

But recording in English had its own challenges for the group. "English isn't anyone's first language, and the only one who can speak English in the group is Wendy," vocalist and dancer Seulgi said, via an interpreter. "So in terms of getting the pronunciation and the nuances right, we got a lot of help from the people around us."

"The demo was in English," she added. "So musically, we tried to express ourselves the way that we heard it [on the demo]."

For rapper and vocalist Joy, the hardest part was figuring out which words needed more emphasis. "The pronunciation is a bit sharper in Korean," she said. "So we had to really think about which syllables to focus on." (And in case you were wondering, yes, even Wendy has had "oh my God" stuck in her head for weeks.)

As K-pop and Korean artists gain visibility and credibility in U.S., the cultural barriers that once prevented these global artists from cracking the Western market are being shattered one milestone at a time. Releasing bilingual songs, or separate English versions, is becoming increasingly popular for K-pop acts, and Red Velvet's global approach to music is paying off. This February, the group will bring their RedMare world tour to the States. The five-city trek across the U.S. — including two sold-out stops in Los Angeles — is a major flex for a Korean girl group. In fact, the last K-pop girl group to tour in the U.S. was Apink in 2016.

"If you listen to all of Red Velvet's albums you can tell that Red Velvet is a group that has a lot to offer," leader Irene said. And arguably it's this variety that appeals most to the masses, transcending language altogether. With their distinct vocal charms and tight harmonies, no two Red Velvet songs sound the same — and while "RBB" may be a divisive entry in the group's discography, you can't say it isn't 100 percent them. Which other group is going to serve horror movie visuals and turn a classic B-movie scream into a perfectly pitched whistle note?

Perhaps Wendy put it best when she said, "The more you listen to our songs, the more you won't be able to resist."