Basilisk: Kouga Ninpou Chou

Basilisk (バジリスク～甲賀忍法帖～, Basilisk Kōga Ninpō Chō?) is a Japanese manga and anime series. The manga was authored by Masaki Segawa and published in Japan in 2003 and 2004, based on the novel The Kouga Ninja Scrolls by Futaro Yamada published in 1958. The anime, produced in 2005 by Gonzo Studios, closely follows the manga aside from a handful of distinctions. The manga won the 2004 Kodansha Manga Award for general manga. The manga was later followed by a sequel series titled The Yagyu Ninja Scrolls which was also based on a novel by Futaro Yamada.

The story takes place in the year 1614. Two ninja clans, Tsubagakure of the Iga and Manjidani of Kouga, battle each other to determine which grandson of Tokugawa Ieyasu will become the next shogun. The deadly competition between 10 elite ninja from each clan unleashes a centuries-old hatred that threatens to destroy all hope for peace between them.

Source: Wikipedia