The Blade of the Courtesans

This Naoki Prize-nominated historical thriller marked the auspicious debut of late-blooming author Keichiro Ryu, who in five years made a name for himself as a master of period novels. In The Blade of the Courtesans, a young samurai by the name of Seichiro Matsunaga, trained in swordfighting by non other than the legendary samurai Musashi Miyamoto, finds himself in Yoshiwara (the pleasure quarters of old Tokyo), per Miyamoto's dying wishes.
In Yoshiwara, Seichiro finds himself defending its denizens against what may be spies from the Yagyu Clan, including one young woman named Oshabu, whose story runs deeper than still water suggests. The Blade of the Courtesans is at once a quiet ode to human liberties in the face of political warfare and edge-fo-your-seat swordfighitng, a Japanese counterpart to the romantic adventures of the medieval knights whose chivalry is rivaled only by their prowess at battle.