When Sunset Shimmer goes to Celestia’s office, the principal wants Princess Twilight to be in her school for one day after the talk she had with her back at the Starswirl Festival. When Sunset gives Twilight her message, the Princess Of Friendship has to keep her word even if Celestia is a principal in the other world. While it’s been a long time she missed Canterlot High, it will be a breath of fresh air. Not to mention Celestia also wants to have a conversation in her office.

Thanks to Daniyel099 for editing this.
https://www.fimfiction.net/user/292246/Daniyel099