When I heard this song, i immediately thought of Jack Frost's little sister.
The beginning is her remembering their last moments, and then it's art from various artists from DeviantArt depicting her and Jack together after the change.

Cruel Reallity - Jack Frost by ~Shoyzz http://shoyzz.deviantart.com/art/Crue...
I'm Sorry... *RotG potential spoilers*by ~TheGothiestFraggle http://thegothiestfraggle.deviantart....
Jack... Is that you?by ~Jadepool929 http://jadepool929.deviantart.com/art...
Safe and Sound by ~tugaMaggie http://tugamaggie.deviantart.com/art/...
i miss you...by ~jackoverlandfrost315 http://browse.deviantart.com/?q=Jack+...
Safe and Soundby ~tugaMaggie http://tugamaggie.deviantart.com/art/...
They believe in me... ...and YOU?by ~Nizcae http://nizcae.deviantart.com/art/They...
Goodbye...until we meet again, my little sister...by ~nikaichan http://nikaichan.deviantart.com/art/G...
Too lateby *Auro-Cyanide http://auro-cyanide.deviantart.com/ar...