Moryo Kiden

From Tokyopop:

Two families, both alike in dignity… and in their hunger for revenge!
When Akaya of the nymphs and Kai of the ogres met, it was love at first sight. Little did these star-crossed lovers know that by their blood, they are born enemies!
They say true love can overcome any obstacle… but can it overcome the wrath of ancient gods and death itself?

Title: Moryo Kiden a.k.a Mouryou Kiden: Legend of the Nymph
Creator: Akiyama Tamayo, CLAMP
Status: Complete
Genre: Shoujo, Fantasy, Drama, Adventure, Romance