Samurai Princess takes place sometime, somewhere in an alternate universe version of feudal Japan, where people live together with highly developed mechanical dolls. However, excessively developed mechanical dolls start causing harm to the human society, leading to ghastly bloodsheds happening all over the place. Under the circumstances, Kyoraku, a mad scientist, creates a female ninja mechanical doll. Equipped with 11 types of built-in weapons, the ninja doll is infused with the souls of eleven of her fallen sisters and she uses their combined power to take down anyone who stands in the way. The ninja doll will not die even if she is slashed by a sword or shot by a gun she is virtually indestructible on her quest to save humanity.