This story is a sequel to Equestria Girls - The Legend of Friendship

After Sunset Shimmer's failed attempt to take over Canterlot High with the help of Princess Twilight's crown from Equestria, things returned to normal in Canterlot High. While everyone was preparing everything for the next upcoming event, Sunset Shimmer was still having trouble to make everyone forget what she did to the students of Canterlot High.

However, there is still something else that has to be taken care of...and it came in form of three girls who seem to possess Equestrian magic...

This story takes place after Season four of My Little Pony - The Legend of Friendship (After Chapter 91) and is a rewrite of the second Equestria Girls movie.
To put it short: The story of My Little Pony - The Legend of Friendship involves around a stallion added to the mane six and several other OC who were added to the original story of Friendship is Magic.
It is advised to read through Chapter 1 - 91 of The Legend of Friendship or at least Equestria Girls - The Legend of Friendship if you want to read this story in the original order but it is not necessary if you don't mind a few OC in this story.