A middle-school girl from the Lion-King organization, Yukina was sent to observe the 4th progenitor and was told to kill him if he becomes a threat. At first, Kojo tries to trick her into thinking he's the wrong person, but his strength is revealed when he intervenes in a fight between her and another vampire. She is constantly following him everywhere he goes and as a result has become very close to him, even allowing him to suck her blood in order for him to gain control over his familiars. Unbeknownst to her, she was actually sent for this very purpose; with the organization intending for her to be his blood partner. Like many others, she was supposedly sold to the Lion-King organization by her parents. By the end of the first arc, she seems to have developed feelings for Kojo.