Basilisk

From Del Rey: By the order of Shogun Ieyasu Tokugawa, ten ninja from the Iga and the Kouga clans must fight to the death in order to determine who will be the next Tokugawa Shogun, with the surviving clan ruling for the next thousand years. But Oboro of the Iga clan and Gennosuke of the Kouga clan have fallen deeply in love. Now these star-crossed lovers have been pitted against each other. Can their romance conquer a centuries-old rivalry? Or is their love destined to end in death? Note: Won the Kodansha Manga Award in the category "Best General Manga" in 2004.