The first half of a new, shorter, but fully written, version of my take on the cancelled Equestria Girls special that was supposed to introduce the human Sunset, with Flash Sentry as the main focus.
Premise:
Flash Sentry has begun to long for the days before Equestrian magic (and Twilight Sparkle) was introduced into his life. He and his family move in next door to the family of his childhood best friend, and Flash transfers to his school to avoid the Rainbooms as much as possible. But as he tries to move on with his life, Flash comes to a horrifying realization that could mean the end of all of reality.