Sihdo and Yayoi are of a private dective agency that watches the attacks of the breeds. Shido is a vampire and Yayoi is his blood source. Upon meeting Yayoi, he meets his little green friend, Guni. Enter Riho, an highshcool student. She loves Shido, but Shido only sees her as annoying girl, until a faitfull night. Finally she is accepted into this tight nit group. Together, the four solve cases of the breeds, saving humanity from the darkness grasp.