Saya Otonashi

Saya Otonashi is an average high school girl, until one day a man named David comes to tell her about her true fate. Saya was adopted and had two "brothers", Kai and Riku.

When she finds out that she is the only remaining original, or the only one left who can kill the chirpoteras, she is taken away from her "family." Along with Hagi, they fight these blood sucking beasts.

Saya is the daughter (if that is even the right word) of a chiropteran named Saya. Saya (the chiropteran) was found by Joel the first with two cocoons in her stomach. Joel took them out to study. He couldn't break the outside, as it repaired itself as soon as it was chipped. Joel cut his finger in the attempt to break them and a drop of his blood fell on one of the cocoons. The cocoon absorbed his blood as soon as it dropped onto the surface. He let blood drip on both of the cocoons and they both absorbed it. Eventually, the cocoons opened and Saya and Diva were born. Joel tried mixing their blood and it crystallized. Joel raised Saya as his daughter and locked Diva up in a tower barely giving her enough food to survive.