Ryder is called off to war in Steurope to run a military base and has to leave his little sister behind with Celestia. Why Celestia? Because Rainbow Dash is in the hospital, Rarity and Sweetie Belle are off in Manehattan. Applejack is.... A tad ticked at Ryder (Translation: She's PISSED at him.) so Scootaloo isn't allowed to stay over until Ryder apologizes for what he did. And Princess Cadence isn't even a good option since she's off in Griffonstone trying to fix something.
Note: This is a first-person fic from the view of Princess Celestia somewhat linked to 'That Night...' and 'Working For Her'.
Added: Teen Gore tag