Buffy the Vampire Slayer: Blooded Christopher Golden , Nancy Holder

Chirayoju, a vampire of Chinese lore, and Sanno, the legendary Japanese Mountain King, have been locked in deadly battle for centuries. 
Literally.
 An ancient curse imprisoned the spirits of these two warriors in an antique sword.

Until the sword arrives in Sunnydale.

Freed by accident, Chirayoju searches for a host body that will allow him to continue wreaking havoc amoung the living and the dead.

Now Buffy's on the trail of this legendary vampire...a bloody trail that leads straight through the heart of the Buffy-Xander-Willow triangle.