Beyond that, this series is not even good as a standard action series. The main character is immortal and can never die no matter how many times he gets stabbed, clubbed or thrown into a huge blender. It doesn’t really matter how strong his opponent is or what technique he is using. The protagonist just stands still and gets hit without caring and waits for the adversary to leave an opening so he can kill him. Basically, he can’t lose while they can, and that makes all the fights boring.
The protagonist is not even cool like Alucard from Hellsing or Dark Shneider of Bastard!! He leaves you with no real impression. Neither do his random enemies and allies. The story is a generic revenge quest you have seen a billion times already, made up of stand alone missions. Plus, it ends without concluding anything.
TL;DR: A passable and forgettable series. Not even the aesthetics of the manga managed to keep me interested for long. The gore was fun and even that fell short when the all mighty protagonist who has no special features could never die.
