There is an organization that helps, or more directs, Saya. They are the ones who placed her with her current family. They know all about her past, but just like Hagi, they won't tell her anything. Mr. David and Nurse Julia want her to remember the information on her own in hopes that she won't go insane. Lewis also works with them. Lewis is the comic relief. He's the one who keeps everyone's spirits up and their bellies full. Their organization is telling Saya that her mission in life, her raison d'Ítre, is to fight the chiropterans.
Now there are actually several different types of chiropterans. The first ones she encounters are blood-thirsty beasts. They have no desires other than to kill for blood. They appear to be created by the military. Then she encounters intelligent, but still very dangerous, chiropterans called Chevaliers. They do drink blood to live, but they can eat human food and appear to be perfectly human, at least until they bite you. They are as devoted to Diva as Hagi is to Saya. The Chevaliers will do anything to protect the mysterious Diva. You might want to avoid reading all of the Wikipedia article, because they do tell you who Diva is in there and why Saya is bound and determined to kill her, and part of the fun of Blood+ is discovering Saya's past along with her. There's another kind of chiropterans called Skiff. We really don't find much out about them in the first half, who created them and why. They're the closest you find to a normal "vampire". They cannot go out in the daylight and must survive on blood to live, but they are intelligent, not blood-thirsty beasts.
Blood+ reminds me of Hellsing, bad-ass warrior taking care of whiney chick. Luckily Saya gets a lot less whiney as it goes on. Once she starts remembering more about who she is and why she fights, she starts to accept it and somewhat stops hiding behind Hagi. The fight scenes are slightly shorter than some animes like Hellsing or Inuyasha even. The fights pretty much boil down to when Saya finally decides to fight, she ends it all. There are very few scenes with fights longer than a minute or two. 100% of the episodes are exciting. They do a very good job of mixing exposition with excitement, so even at the beginning when they're setting the story up, you still don't get bored. The translation is also quite good. Instead of being literal, it makes logical sense, so you don't end up with Engrish. The graphics are simple, but beautiful. The water especially is just plain amazing. I loved the way they make the ocean look. It's so lifelike I'd swear it's a real image and not drawn. The DVD set also includes a full disc of interviews with the cast and crew.
We really loved Blood+. It's got everything you could want, action, adventure, very little romance, and quite a lot of interesting characters. It is a little confusing to try and figure out what's going on at the beginning, but like I said before, it's wonderful to be able to discover Saya's past along with her. I would definitely recommend everyone who likes anime to check this one out. Now I've just got to wait on the second part to find out what happens!