David

The character, David, appears in both the movie Blood: The Last Vampire and the series Blood Plus. However, it is not the same person. The David in Blood Plus is the son of the character in The Last Vampire. Both men are members of the Red Shield organization. Other than Hagi, some members of Red Shield, including David, know the truth about Saya's past and her connection to the Chiropterans. 

David is a devoted member of Red Shield and being a former member of a Special Forces squad, he coordinates many of their attacks and operations. While he is human, he is very capable of handling himself in a fight, and is not afraid to fight the Chiropterans. His preferred weapon is his trusty pistol.

Initially, David comes across as a somewhat cold character, and it appears that he sees Saya as merely a tool to use against the Chiropteran. However, underneath his hardened exterior, he does care for Saya's safety. He also becomes attached to Saya's foster brothers, Kai and Riku, and helps them to come to terms with what Saya is. In particular, he takes more of an interest in Kai, most likely because he sees a younger version of himself in Kai.

While he mostly comes across as an emotionless man who is devoted to his duty and nothing else, his human side mostly comes across in his relationship with Julia Silverstein. Julia is a medical doctor with Red Shield, and David has a great deal of affection for her. While he never tells her outright how he feels, it is obvious to Julia and the feelings appear to be reciprocated.