Shizuka Hio

Shizuka Hio (緋桜 閑 Hiō Shizuka) was the first antagonist to appear in Vampire Knight. Shizuka was the Pureblood vampire who bit Zero, as well as the vampire responsible for killing his parents and bringing Zero's brother Ichiru  to her side. She is regarded as dangerously erratic and insane, garnering her the epiphet "Kuruizaki-Hime" (狂い咲き姫  "Flowers blooming out of season princess"). Shizuka shows up at Cross Academy in the guise of another vampire, Maria Kurenai, but is recognized by both Kaname and Zero. In order to save Zero, Yuki risked her life and humanity for Zero to be able to drink Shizuka's blood to prevent his fall to Level E, but Zero stops her by defying his master's orders. Yuki, in turn, prevents Zero from gaining his revenge on Shizuka, and Kaname kills Shizuka to save Yuki.

It is later revealed that Shizuka had been used by a number of vampires for their own purposes. Out of hatred for her fiancé, Rido Kuran, she had sought more power to kill him and refused to submit to him. When she began having a vampire who had once been human as her lover, Rido deliberately arranged for her lover to be listed amongst the Level E vampires to be eliminated, in spite of the fact that Shizuka's lover was in no danger of falling to that level. Shizuka's lover was killed by the Kiryu family, though she was not offered the chance for revenge until Kaname released her from her cage. When Zero learns that Kaname was responsible for releasing Shizuka from Sara Shirabuki, Kaname claims that he had done so for Shizuka to take revenge on the Kiryus, which would ensure that their twin sons would seek the elimination of all Pureblood vampires.