Each of the previous Sekaiju no MeiQ (Etrian Odyssey) projects (as well as 7th Dragon) had a small promotional album with exclusive arrangements, B-Sides, outtakes, etc. This is that album specifically for the third game in the series.
Of all those mini-albums released in the past, I found this one to be the least interesting. The piano tracks didn’t grab me, and neither did the cut music. Fortunately, I don’t think this disc is representative of the OST proper, which I found to be a strange and refreshing take on “retro” music from Koshiro-san.
Again, this is a Japanese promotional item. Unless you’re into importing full games, it’s unlikely you could get this soundtrack anyway. But completionists will go to dire straits, and if you’re one of those, check out Yahoo! Japan Auctions for a chance at owning this mini-album.