I have been searching for this forever. I swear I've listened to every song on the soundtrack multiple times trying to find the song used in the ending cutscene.
There are two parts specificially that I must find:
1) Starts at 1:04 (in the video linked below). The melody is the same as part of Reunion, but it's played through some trible flute thing as opposed to the Chinese instrument from Reunion. It's so peaceful... i must find it ;_;
Unfortunately since it's just a variation from the same melody as Reunion, I have a feeling it might not be in the soundtrack. However the next one should be since it's unique.
2) The part from 3:28-3:44 (again in the video below). Speficially the part that starts at 3:37. This one is a unique melody so I'd assume it's be somewhere in the soundtrack.