BLOOD+

Blood+ was inspired by the 2000 anime film Blood: The Last Vampire; however, there are only a few allusions and basic elements from the film. Fujisaku has been involved with both works, including acting as the director for Blood+ and writing the novelization of Blood: The Last Vampire.

Under the care of her adoptive family, Saya Otonashi has been living the life of an anaemic and amnesiac, but otherwise ordinary schoolgirl. Saya’s happy life is shattered when she is attacked by a chiropteran, learning that she is the only one who can defeat them.
Armed with her katana, Saya embarks on a journey with her family, allies, and her chevalier, Hagi, to rid the world of chiropteran and rediscover her identity. The course of the journey reveals the background history of the chiropterans and Saya's very deep past, which extends into the mid-19th century.

Haji first met Saya when he was a child of age 12 and was brought by Joel to be her companion and hopefully mate and create more specimens someday. At this time Saya was 43 although she doesn't appear to be since she stopped aging in 1863. He lived with her in Joel's mansion for many years. But one day he fell from a cliff in an attempt to pick a flower that Saya wanted as a present for Joel's birthday. Seeing him bleeding everywhere and not really understanding that people don't drink blood to remain healthy, Saya gave him her own blood. Thus she unwittingly turned him into her "Chevalier."

The series is initially set in present day (September 2005) Okinawa City (Koza), on Okinawa Island, near the US Kadena Air Base. In the course of the series, Saya visits locations across the world, fighting enemy chiropteran and searching for her origins...And realising a terrible mistake she made in the past that has led to the rise of the chiropterans... A mistake she herself named as Diva,her little sister...

Saya's twin sister and the story's main antagonist,Diva. She provides the Delta67 (derived from her blood) which is used to transform people into Chiropterans. When she was born she was kept in an isolated tower as part of an experiment. Because of that she hated Joel, such that when Saya freed her she slaughtered him and the people at his birthday party. Her isolation left her childish and socially inept as well as ignorant of the moral ramifications of her actions. It is also hinted that Diva only wanted a family just like Saya's.

I must admit that the anime was pretty boring in the beginning but it did have certain unexpected twists as it progressed which helped to me remain hooked to it till the end without missing a single episode of the 50 episodes long anime....