The Swordswoman Hardcover – January 1, 1982 by Jessica Amanda Salmonson
 
Kendo is a thing of the spirit, or so Erin Wyler thought of the ancient art of Japanese sword fighting--until the day in the fencing hall when her bamboo sword was transformed into a supernatural steel blade and her sparring partner became a loathsome demon. Suddenly kendo had become a thing of madness.