Blood: the Last Vampire: Night of the Beasts(2000)

Blood: the Last Vampire: Kemonotachi no Yoru

This novel is set in Japan in the late 1960s, where the youth are organizing a violent uprising against the government. Part of this revolt is the politically active student, Rei, whose fate is one day, coincidentally, bound to a mysterious girl, Saya. An exciting criminal case, and a voyage into the discovery of vampirism, takes its course.