Larva

Larva is the Shinma (in Japanese shinma means "demon and god") who forced Miyu to become a vampire. He is one of the Western Shinma. He was sent to kill her before her vampiric blood awakened, but Larva became attached to the little girl. He waited too long to kill her. When he finally tried, Miyu's vampiric blood awakened and she took his blood. Because of this, he is bound to her. She has sealed his face and voice behind a mask and keeps him as her servant and friend. Before being locked away, Larva was a cold and malicious demon, but he becomes attached to Miyu after he is bound to her. He sympathizes with her and defends her, even against those who would free him by being rid of her. He is not really a prisoner (I don't know why he doesn't leave; perhaps its a feeling of debt toward Miyu). When Larva falls ill, Miyu is forced to turn to Himiko, her most dangerous enemy, for help. But she does it, and makes it clear that she will do anything for Larva.

Later, in the manga series, Miyu's blood is removed from Larva by Carlua. He loses all memory of her and returns to his former self; he fights on the side of the Western Shinma. Eventually, he faces off against Miyu and kills her himself, as she is too stunned by his betrayal and defends herself weakly. Then she is revived by Yui and she and Larva later return to their former relationship. His real name is said to be unpronouncable, so he adopted "Larva". Larva means "mask, spirit, or ghost".