Oniwaka to Ushiwaka - Edge of the World

From Simple Scans:

Set during the late Heian era eight centuries ago, when the Taira samurai clan held power and just before the rise of the shogunate in Japan. This historical fantasy re-imagines the adventures of the real-life samurai leader Minamoto no Yoshitsune (Ushiwaka) and his loyal warrior monk Musashibou Benkei (Oniwaka).