The title track "Mysterious" is written by Simon Janlöv (SHINee's Married to the music & Chocolate, VIXX's Chained up, KAT-TUN's 楔 -kusabi-) and Ylva Dimberg (NCT127's Fire Truck). The other three songs have been previously released as digital singles. You can listen to them here:
With such great songs this mini album is bound to be a hit!
Source: Fantagio music, All music, Sound graphics
12.30-Concept Teaser #1
01.02-Concept Teaser #2
01.04-Track List Mash-up Teaser