When a small village succumbs to a terrible plague, a team of ninjas are sent to investigate, and realize that all is not as it seems. Jubei saves her from a fate worse than death, and unwittingly becomes drawn into the web of treachery. He is soon faced with his greatest challenge - an enemy for whom death holds no fear, with the power to destroy Jubei's world. In my humble opinion, this anime is the best that Yoshiaki Kawajiri has ever done. Ninja scroll is beautiful.
Animation flows, the character design is great, and fights are well choreographed.
The most impressive thing, though, is the swordsmanship of the main character, Jubei. The type of sword he carries gives me this feeling, as well as the way he uses it. This kind of attention to historical accuracy in technique, even in a fantasy style backdrop, is something that I like a lot. The plot is less amazing than the animation, but it's still good. The demons are mostly there to provide our hero with opponents.