Princess Celestia has no problem with leaving the three Sirens in the realm across the mirror, in effect dumping her own world’s problems on another world. Princess Twilight Sparkle makes regular visits. Sunset Shimmer, while redeemed and intent on staying there, is still a foreigner to the human realm. Sunset knows this status quo can't last, especially after not one but two schools know about magic following the Friendship Games.
Sunset soon decides that, if Equestria has no problem with its own citizens visiting other dimensions, it better be prepared to allow the reverse. Thus begins Sunset's Extradimensional Tourist Agency.
What freaks her out is just how many people adore the idea of temporarily becoming magical coloured ponies.
Other Characters tag includes the Shadow Five. Sex Rating will be for innuendo and references.