In a world where vampires exist, Saki Fujimiya is a vampire hunter. While she attends school like a normal teenager, she targets a specific vampire in her free time. However, when Saki confronts the vampire, none of her attacks are effective, giving her enemy an opportunity to drink her blood. The vampire—using the name Miyoko Kujou—claims that she has no intent to kill Saki before declaring that she actually loves her. The encounter ends there, but Saki continues to face Miyoko at school.

Miyoko has made a habit of drinking Saki's blood, and while she may say otherwise, Saki quickly succumbs to pleasure. Despite the gratification she receives from this interaction, Saki always tries to kill Miyoko immediately afterward. Is this a sense of loyalty to her position as a vampire hunter, or is it something else entirely?