RG Veda

Both have ancient emperors in a magic east land. the fate of this world also depends of a girl. sword wielding. 

Both are adaptations of CLAMP works. Both anime have similar concepts about destiny/revenge/changing ones fate. Both adaptations rush through a story that can't possibly be told completely in the time given, resulting in lots of cut content from the manga/original scenes that change the outcome of the story to fit into a shorter narrative.  

It's by CLAMP also. The characters in X, Tokyo Babylon, RG Veda, xxxHolic, Tsubasa Chronicle, and Chobits all...connect. The shows sort of overlap. 

both are shoujo action 2 episode ova with a slightly romantic shounen ai main couple with huge age gap. 

both are romantic fantasy adventure shoujo about a weak main character who's being protected by very powerful and beautiful guardians. 

Expect wizardry and medieval fantasy in both