A team of Ninja known as the Koga ninja Team are sent out to investigate the deaths, but before they can reach the village they are ambushed in the trees by an amazingly powerful enemy in the shadows, and all savagely mutilated... except one. A female warrior named Kagero.
She is taken by their attacker only to be saved by our hero, Jubei. She thanks him and pretends to be strong and indifferent, but after he leaves, Kagero's pain is shown. Through out her entire life she has been treated as nothing more than an expendable warrior... living in a world void of emotion and overflowing with pain.
In turn for Jubei saving Kagero (and later dispensing of her attacker) the rest of the Devils of Kimon come after him and he is unwillingly hired by a shrewd old ninja spy named Dakuan. Together, Dakuan and Jubei end up teaming up with Kagero to battle these demons with super-human abilities.
Here's a quote from the creator of Ninja Scroll
When asked about the myriad of shape-shifting supernatural beings that populate his anime, he replies: "I'm interested in the impact of horror created by blending reality and fantasy and so I like designing creatures that are half man and half beast. I often use these creatures in my work because only through animation can they truly exist - in the animated worlds I create they are living, breathing creatures in their 'natural' settings."
Kagero
Dakuan
Hanza
Chamberlain
Gemma
Yurimaru
Tessai
Zakuro
Benisato
Shijima
Mushiza
Mujuro
