"Dream Sky" was written and composed by Song Seunghyun, with additional composition by Choi Minhwan.

was released on July 27, 2011, in three editions: CD and DVD Type A which included footage from two release events of their fourth single "Satisfaction" and one release event of their second Japanese studio album Five Treasure Island,[2] CD and DVD Type B which included the music video to "Let It Go!"

[4] On August 7, the band performed on Fuji TV's annual FNS Music Festival.

went on to sale over 41,500 copies in Japan.a On the issue dated August 13, 2011, the song debuted and peaked at number six on the Billboard Japan Hot 100.

[10] On the Recording Industry Association of Japan (RIAJ) Digital Track Chart, the song debuted at number 71.