Kojou Akatsuki[]
Yukina was sent to observe the Fourth Primogenitor, Kojou Akatsuki, by the Lion King Organization, with the order of eliminating him if he was to become a threat. She is constantly following him everywhere he goes and as a result she 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 Lion King Organization intending for her to be his first blood partner, and even his mate. By the end of the first arc, she seems to have developed feelings for Kojou. In the Strike the Blood EX side-story, and later in Volume 17 of the light novel series, it is revealed that Kojou has made Itogami Island his Dominion as the Fourth Primogenitor, properly named Empire of the Dawn, and he has a daughter with both Yukina and Asagi, Reina Akatsuki and Moegi Akatsuki, respectively.
Sayaka Kirasaka[]
She's Yukina's childhood friend, ex-roommate and a War Dancer from the Lion-King. She is over-protective towards Yukina.
Nagisa Akatsuki[]
Nagisa is Yukina's classmate and close friend. She is usually chatty with people she likes, including Yukina. When Yukina learn the truth past from Kojou about Nagisa false past, they decide not to telling her about this. And decide telling the truth to her when the time has come.
Kanon Kanase[]
Astarte[]
Natsuki Minamiya[]
Misaki Sasasaki[]
Mimori Akatsuki[]
La Folia Rihavein[]
Kiriha Kisaki[]
Yuuma Tokoyogi[]
Reina Akatsuki[]
Yukina and Kojou's daughter. Reina greatly resembles her mother in appearance.