"Blood+" is a manga series that expands on the narrative of the 2000 anime film "Blood: The Last Vampire." The story centers on Saya Otonashi, a seemingly ordinary high school girl living in Okinawa with her adoptive family. Saya suffers from amnesia and has no recollection of her life before being found unconscious on a battlefield years earlier. Her peaceful existence is disrupted when she encounters a Chiropteran, a monstrous creature that feeds on human blood. During this encounter, Saya’s latent abilities awaken, revealing her true identity as a powerful warrior destined to combat the Chiropteran threat.

Saya learns that she is part of an ancient bloodline of beings known as "queens," who are tasked with eradicating Chiropterans. Her blood possesses unique properties that can destroy these creatures, and she wields a katana as her primary weapon. As Saya begins to recover fragments of her memory, she discovers her connection to a secret organization called the Red Shield, which has been monitoring and combating Chiropterans for centuries. The Red Shield assigns Saya a chevalier, a human companion bound to protect her, named Hagi, who is deeply loyal and shares a mysterious past with her.

The narrative follows Saya’s journey across multiple countries, including Japan, Vietnam, Russia, and France, as she battles Chiropterans and uncovers the truth about her origins. Along the way, she encounters allies and enemies, including Diva, another queen who serves as her primary antagonist. Diva, unlike Saya, embraces her role as a predator and seeks to create a world dominated by Chiropterans. The conflict between Saya and Diva is central to the story, as their intertwined fates and shared bloodline drive the narrative forward.

Saya’s relationships with her adoptive family, particularly her brother Kai and younger sister Riku, add emotional depth to the story. Kai becomes increasingly involved in Saya’s battles, while Riku’s vulnerability highlights the personal stakes of Saya’s mission. The series explores themes of identity, sacrifice, and the consequences of wielding power, as Saya grapples with her dual nature as both a protector of humanity and a being whose existence is tied to destruction.

The manga delves into the origins of the Chiropterans, revealing their creation as a result of experiments conducted by a secretive organization. It also examines the moral complexities of the Red Shield’s operations, as their methods often involve ethically questionable decisions. The story builds toward a climactic confrontation between Saya and Diva, with the fate of humanity hanging in the balance. Through its intricate plot and character-driven narrative, "Blood+" combines action, mystery, and emotional resonance to create a compelling tale of survival and self-discovery.