Following the release of the album tracklist, CLASS:y unveiled the highlight medley revealing the melody of all the tracks.

On October 20 at midnight KST, the rookie girl group teased all the tracks from their 2nd mini-album. Both tracks - "Tik Tik Boom" and "ZEALOUS" - have an upbeat, powerful melody showing the charisma of the girls.

Meanwhile, CLASS:y will drop the album and music video for their 2nd mini-album titled 'Day & Night' on October 26.