Blade of the Immortal (Mugen no Jyuunin)

[Stuart]

Blade of the Immortal is the story of the ronin (masterless samurai) Manji, once in the service of Lord Horii Shigenobu, until he became disillusioned with his life and the code of the samurai after he discovered that that criminals he had been killing on Horii's orders were really farmers trying to contact the local authorities to inform them of Horii's misuse of taxes. Manji killed Horii in return, and then killed 99 police officers who attempted to bring him in, including Saito Tatsumasa, whom Manji slew in front of Saito's wife, Machi... who just so happened to be Manji's little sister.

 

At some point after this incident, Manji encountered Yaobikuni, who fed Manji the Kessen-Chu ("bloodworms" - they heal virtuall any damage he suffers, bar decapitation) to make him immortal. Now, unable to be killed, Manji felt he was more monster than man. He also felt his skills degrading as he realized he couldn't be killed in a fight, and thus didn't need to fight a well as he had before.

 

After killing the fake priest Gyobutsu Johnny, Manji ran afoul of the Shinsen-gumi, "the world's baddest ronin gang." Their leader, Shido Hishiyasu, killed Machi in revenge for the death of Johnny (who was his brother). Unfortunately for Shido and the rest of the Shinsen-gumi, Manji then cut all of them down. Upon returning to Yaobikuni, he made her a deal. He'd kill 1000 evil men as penance for the 100 innocent lives he took, and in return, she'd give him the release of his own death.