The title song “Fantasy” was written by songwriter Kim Mi-jin from Music Cube and VIXX member Ravi. The song was composed and arranged by Devine Channel.

The track has a “dramatic, orchestral sound” with an “elegant [and] ethereal quality” along with Ludwig van Beethoven’s most popular pieces, “Moonlight Sonata”. “Fantasy” is in line with the boy band’s dark-tinged past releases, “Eternity,” “Error,” and “Voodoo Doll”, but is a creative upgrade with a harder emotional punch and demanding vocal performance over a cinematic production.

The accompanying music video also plays to the band’s shadowy sentiments with muted-colored clothing and imagery of thorns and spikes.