These people--even the protagonists Rin and Manji--are insane and ruthless.

Too little or shallow character motivations and plot holes. Yaobikuni's motivations to give Manji the kessen-chu aren't shown. The question as to what method to use to figure out who the truly evil ones are was completely dropped. It wasn't shown that Sori felt guilty and used the excuse to pay Rin for X because he could've simply taken X. ( )

2,5-3 ( )

Well done, I guess, but not really my thing. The details of the cynical antihero's curse of immortality are sort of novel (body parts made out of "blood worms", and the requirement that he find and kill exactly one thousand bad guys) but the fight scenes fall into a predictable pattern: bad guy chops off hero's arms/legs/liver, not realizing he's immortal; bad guy chuckles and turns to go; hero gets up and kills him. Also, samurai intrigue for its own sake (renegades from Sword School X form Sword School Y to wipe out all the other sword schools, etc.) is possibly even sillier than superhero intrigue. The art is lovely, although the very gory violence is stylized in a way that just looks odd to me: for instance, people don't just get stabbed or sliced by swords, they get sliced in half effortlessly as if they were made out of Jello. ( )

immortal swordsman must kill 1000 evil men to be released

This is a very fun, very good manga, though one that's exceptionally violent. ( )