After kicking off the year by falling in love with a "Rookie" and then giving Korea a summer hit with "Red Flavor," Red Velvet is back with the most Perfect Velvet side of themselves yet with their second full-length album and a brand new single, the taunting "Peek-A-Boo."

Released on Friday (Nov. 17), the 9-track Perfect Velvet presents a mature take on what it means to be Red Velvet, a K-pop girl group whose career has been shaped by a split-sonic identity: their “red” songs are bright and upbeat, while their “velvet” ones offer up a smoother sound. The quintet veers towards the former on most of their singles and EPs releases, but the new album serves as a counter to 2015’s The Red, Red Velvet’s first full-length album that showcased the group’s colorful side on what was one of the best K-pop albums of that year.

“This year we showed a lot of red style, and it’s been very bright,” Irene told Billboard over a video call from Seoul days before the release of their genre-hopping album Perfect Velvet. “But, as the title of the new album suggests, we feel like we want to show a more perfect side to ourselves, more perfect music. An upgraded version of what we can show of the velvet concept.”

Coming just a few months after their vibrant “Red Flavor,” which topped Korean charts and hit No. 4 on the World Digital Song Sales chart after it was released in July, the five women of Red Velvet -- Irene, Wendy, Seulgi, Joy and Yeri -- admitted to being a tad nervous about presenting a new song so swiftly on the heels of such a success. “‘Peek-A-Boo’ is a really addictive song,” said Wendy, the group’s primary vocalist and only fluent English-speaking member. “Because it’s a really good song we are pumped up. We are kind of under pressure because [of] ‘Red Flavor.’ But I think we’ll be fine.”

While still an upbeat dance track, "Peek-A-Boo" is less bubbly than this year’s other singles from the Red Velvet. It instead reveals a more sophisticated, mature sound through its woozy synths, tinny beats and creeping, playful vocals, along with a seductively murderous music video that shows the girl group at their most sensual -- a nod to the "velvet" concept.

And it’s not only the single that emphasizes an alternate to the bright image the fivesome have showcased throughout much of 2017: Several tracks on Perfect Velvet, like “Look” and “Attaboy,” feature positive, millennial-focused messages about pursuing dreams and Yeri wears a rainbow shirt bearing the phrase “Love sees no colour” in the music video -- all nods to the group reflecting on the world around them. “We have our [social media accounts],” said Wendy. “Whenever we look at them, there are a lot of fans. We just wanted to reflect the emotions that are going on with the people. We wanted to show them that we are feeling the same feelings [of people] with the same age as our group and connect with them through our songs.”

Changing things up stylistically was a bit of a struggle, with Wendy admitting she had a hard time getting into character as a serious femme fatale while on set filming the music video for “Peek-A-Boo,” though Seulgi liked the alternative, darker pop sound and eerie music video. “I felt like I was part of a horror movie,” she said. “I kind of felt that it really matched our style this time around.” Compared to “Rookie” and “Red Flavor,” she added that she felt the new single shows a more charming side to Red Velvet. "I feel like people will be more curious about it because it’s mysterious and charming all at the same time.”

With a bit of black magic in the music video for “Peek-A-Boo” and an overall lush pop sound throughout Perfect Velvet, “mysterious and charming” is the precise way to describe their latest release, which the group hopes will close out a year full of big moments in the right way. “Because the album title is Perfect Velvet, I think this album is really good to be released before 2017 ends,” Wendy said. “It can show the perfect Red Velvet performances and songs. I think that it’s good timing. I think it’s good to end perfectly at the end of the year.”