Blade of the Immortal is the story about Manji (also known as "twelve blades"), the samurai who has killed innocent victims on his master's orders. However, he eventually realizes that his master wasn't as good a guy as he thought, and kills him. Killing one's superior isn't very legal, and Manji finds himself one of the most wanted persons in Japan.

Several police officers try to capture and kill him, but only manage to end up as fodder for Manji's swords. After slaying a hundred officers, he is tired of living and wants to die, but he can't. Not until he has atoned for his slaughter. To make up for the hundred people he killed, he must now kill a thousand more. The story takes place in the 2nd year of Tenmei, which is approximately 1782-1783 in Gregorian years

Here's a list of some of the important characters in Blade of the Immortal:

  • Manji: The main character of this story, is a ronin, a masterless samurai.
  • Yaobikuni: means "nun of eight-hundred years," is the eight hundread-year-old nun who made Manji immortal by secretly feeding him kessen-chu, the sacred bloodworms.
  • Machi: Manji's little sister.
  • Saito: He used to be Machi's husband before Manji made her a widow.
  • Anotsu: Is the master of the Itto-ryu sword school, a school that has as its motto "the way of the sword is the way of victory!"
  • Asano is the master of the Myutenichi-ryu sword school, which he inherited from his father. He was killed by Anotsu.
  • Asano Rin: is the daughter of the dead master of the Myutenichi-ryu sword school.