16th century Japan. The fates of warlords ebb and flow like tides of blood, none more than the Aragami Clan who follow their lord clad in the 'Red Devil' mask into every battle. But when Lord Aragami succumbs to illness, his daughter, the fierce Ketsuko, hatches a plot to save her people, no matter the cost...

Years later, as Ketsuko wanders the heaving battlefields of her ruined homeland, she discovers a chance to avenge the terrible wrong done to her clan, even if it means stepping back onto a road steeped in slaughter.