Bloody Cross

Bloody Cross (ブラッディ・クロス) is a manga series by Shiwo Komeyama. It was serialized in Shounen Gangan.

Plot
Half angels: Individuals cursed because of their impure lineage. Tsukimiya is a Vampire Half Angel, and with her companion-of-convenience Hinata, with whom she shares a strained relationship at best, and an antagonistic one at worst, are on a search for the "God's Book of Prophecy." The book harbors immense power, and is supposedly the only thing capable of removing the half-blood curse that Tsukimiya and Hinata share.

The problem is that nobody knows if the book's power is enough to save two people, and neither is willing to share with the other.