Blood+ - City of the Night Walkers

In Hong Kong, Nishi is a young policeman investigating a case of strange murders, where the victims appear to have died of fatal blood loss. But the investigation is taken over by a mysterious organization, whose members warn Nishi that he had better not keep on trying to uncover the truth. Some time later, as Nishi wanders in the city, he is suddenly attacked by a monster; but a beautiful stranger saves him.