Framed for murdering her parents, Twilight Sparkle was exiled from her own world with Spike, who was one of two others who knew the truth, minus the real killer. The world that the two had wound up in was the world of Undertale.
Luckily, it was on a True Pacifist run, and luckily, Frisk was the one who found them.
After the barrier is broken and the monsters were freed by Asriel Dreemurr, Twilight and Spike find themselves in the surface, where they were adopted by Toriel (and Asgore) along with Frisk. Now, these two will be growing up in this new world along with Frisk and a revived Asriel.
Watch as they go through their new lives in Earth, and wonder just what the future holds for them.