Blood+ is a manga created by Asuka Katsura and was published in Monthly Shonen Ace by Kadokawa Shoten starting December 26, 2005 and ended April 26, 2007. An anime adaptation was made by Production I.G and was directed by Junichi Fujisaku. It aired starting October 8, 2005 and ended September 23, 2006 on TBS and Animax. Two Japanese light novels were written by Ryo Ikehata and illustrated by Chizu Hashii. The first novel was released on May 1, 2006 and the final one was released on May 1, 2007.
Otonashi Saya is an anemic amnesiac who lives with her adoptive family. She was an ordinary girl until she was attacked by one of the Chiropteran, arms herself with a katana and learns that only she can defeat them. She goes on a journey with her chevalier, Haji, allies and family to wipe out the Chiropteran and retrieve her identity. Her journey reveals the origin of the Chiropterans and Otonashi Saya’s past.
Otonashi Saya – Saya is an ordinary girl living with amnesia and because of her anemia, has to have regular blood transfusions. Her memories return after she is attacked by a Chiropteran and a mysterious man feed her his blood. After this, her appearance changes by the reddening of her eyes and the darkening of her lips. She gains enhanced power and speed and she is given a katana with her blood on it to slay the Chiropteran because her blood has special properties.
Haji – Haji is Saya’s Chevalier. He begun as Saya’s servant but at one point, he almost dies after falling off a cliff. To save him, Saya fed him her blood turning him into a Chevalier, a kind of Chiropteran whose role is to serve his queen Chiropteran. He no longer needs to sleep or eat and watches over Saya.
Miyagusku Kai –Kai is the eldest brother of Saya’s adopted family. He doesn’t have special abilities but he does what he can to protect Saya and their youngest sibling, Riku.
Miyagusku Riku – Riku is the youngest brother of Saya and Kai. At one point, Riku’s blood is drained by Diva because he mistook her for Saya. To save him, Saya makes Riku a Chevalier but in the process, makes him able to reproduce with Diva. Diva rapes him to create offspring and kills him afterwards.
Diva – Diva also has the same powers as Saya as she is her younger twin sister. She was a test subject for Joel and was isolated in a tower where she was given only the essentials for living such as food and water as well as regular blood transfusions. The only person she interacted with was Amshel, her caretaker.