Courtesan and the Samurai. The Shogun Quartet, Book 3, Paperback/Lesley Downer

When enemy soldiers attack her house she flees across the shattered city of Tokyo and takes refuge in the Yoshiwara, its famous pleasure-quarters.There she is forced to become a courtesan.Yozo, brave, loyal and a brilliant swordsman, is pledged to the embattled shogun.