Shizuka Hio (緋桜 閑, Hiō Shizuka?) is the pureblood vampire who bit Zero; even her fellow vampires are uneasy around her and refer to her as the "Madly Blooming Princess". A manservant whom she loved (a former human vampire, falsely classified by the Hunter's Association as Level E) was assigned to be killed by a Kiryu vampire hunter. Enraged and vengeful, she attacked the Kiryu family, killing both parents, biting Zero (which subsequently turned him into a vampire), and taking Zero's twin, Ichiru, in as a devoted servant. She was originally Rido Kuran's fiancée, but they never married due to his disappearance and finally her death.
Because Shizuka's blood can prevent Zero from falling to Level E, Yuki once had risked her life and humanity for Zero to be able to drink Shizuka's blood. However, to protect Yuki, Kaname kills Shizuka and drinks her blood, leaving only a small amount for Zero to drink. Unfortunately the blood is drunk by Ichiru, who arrived to find Shizuka first. Before dying, Shizuka warns Kaname that he will live in darkness and has summoned a sinister future for himself for drinking the blood of a Pureblood, when he is one himself.