One song, two tracks: vocal and instrumental. "白日夢" (Daydream) by Rekka Katakiri is a single release tied to an Xbox 360 title. The vocal version carries that specific Japanese game vocal style, earnest and atmospheric. The instrumental lets the arrangement stand alone.
Read more
Not much to analyze with a two-track single, but single releases like this were a standard part of the Japanese game music ecosystem around 2010. The title "Daydream" implies something wistful and transient, and the music presumably delivers on that mood.
If you're collecting Rekka Katakiri's discography or tracking down every vocal single from this era, here's one more for the archive.