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Yoo Hee Yeol revealed, "Akdong Musician's Suhyun sang this song and she is the youngest out of everyone I've worked with. When I first made the song, it was at a time when I was reading a Japanese Manga and the story relates to the song as it's about a little girl protecting the earth. But when I had Yoon Sang listen to it in the studio, he told me that it sounded like a Christmas song." 

He continued, "When I had Lee Gyu Ho listen to it, he also told me that it felt like a winter song. And when I looked at the lyrics, it was too much like a fairy-tale story so I had trouble choosing a singer. Female singers around me are all in their 30s." 

Despite the dilemma of searching for the perfect vocalist to sing such a youthful track, with the help of an acquaintance, Yoo Hee Yeol was able to bring on Suhyun to his list of collaborators for the album. 

He said, "After I thought about it for a while, my manager's friend recommended Akdong Musician's Suhyun. When I thought about it, there's only a handful of artists who can sing a song with such lyrics." 

Yoo Hee Yeol continued, "Fortunately, I worked with YG (Yang Hyun Suk) for 'K-Pop Star.' I heard that YG has no plans on working with outside artists for a while so I expected to get rejected. But he happily accepted, and thankfully I was able to complete the song." 

Meanwhile, 'Da Capo,' featuring talented vocalists such as Suhyun, is set to be released on November 18.