It's the first Hearth's Warming after Twilight's coronation, and Starlight notices that Twilight has been overworking herself. She wants to make Hearth's Warming perfect, so she enlists Sunset's help...
Starlight invites herself back to the human world, and asks Sunset to come along. Anything and everything that follows is entirely on their shoulders. Or maybe not.
After dating for almost a year, Sunset and Gilda are finally moving in together. Dating is one thing, though, while the prospect of living together, especially with both of their tempers, is an entirely different beast.