Equestria is now the Empire of the Rising Sun.

Twilight & Shining's Dad is the current Shogun, Celestia is Empress (or Princess, whichever works) by virtue of being the direct descendant of the sun godess… by…. being the sun godess… No objections there.

Twilight Sparkle, heir of the current Shogunate, is sent to a neighbouring clan in a formal hostage exchange to ensure loyalty and good relations in some very turbulent times. And soon realises things are not quite as they seem to be in quiet Ponyville Castletown.

But first some massive prolouging while I get some sleep.