A man with an immortal body must destroy 1000 evil men in order to relieve himself of the curse of eternal life.
Manji is a skilled samurai who learned that his master was using him to enforce brutal laws on the local village. In anger he killed his master and the other 100 samurai who tried to protect him. After this he met an elderly nun who cursed him: Manji's blood is full of strange worms who restore his body whenever he is injured. In order to relieve himself of this curse and be permitted to die, Manji swears that he will kill 1,000 evil men to make up for the 100 good samurai he killed.
Before long he meets Rin, the daughter of a swordfighting family whose school was massacred by a man named Anotsu and his Itto-Ryu school. She requests that he act as her bodyguard and help her get revenge on the Itto-Ryu school, leading Manji on the start of finding 1,000 evil men.