Janus: Oni no Ichizoku

The manga centers on Kiichi Samonji, a descendant of the warrior monk Kiichi Hougen. Kiichi Samonji is also a loyal retainer of the historical daimyo Imagawa Yoshimoto, the legendary "number one Daimyou in the Toukaidou." In the fateful battle between Imagawa and rival Oda Nobunaga in the Battle of Okehazama that would result in Imagawa's death, Imagawa gives Kiichi one final order.

(Source: ANN)