You are determined not to see it though, so that is hardly surprising -- psychologists determined a long time ago that humans have a tendency to look for what proves them right rather than what proves them wrong. It's called confirmation bias. It especially applies to art, where only rigorous analysis can determine if a work has the nuances and particulars vital to great works, and a person suffering from confirmation bias will not be willing to overcome the mental-emotional obstacles necessary to find these bits and pieces.I'm sorry, but I can't help but pick on the stupidity and immaturity of this. First of all, mutated vampires. Like I said, childish cartoons. Second of all, targeted for revenge. Pointless confrontation, especially because he isn't dangerous to them anymore? And third of all the idea of a hidden city where vampires and humans coexist. Vampires suck blood! According to all vampire stories it's like an overwhelming desire! And, assuming humans don't like vampires sucking them dry, the idea of a city where they could coexist is ridiculous.
I'm sorry phoneix, I'm just not seeing it.
Not that I can say whether this series suits me or not, as I have never seen it -- there is plenty of anime I do not like at all. This could be one of them, or it could not.
However, phoenix made a good point about vampires. The version you described is the one-dimensional and rather uninteresting variety. If anyone tried making Vampire films like that after Underworld, audiences would laugh (or yawn). Vampires nowadays need to be sophisticated and complex in their dealings with humans.