Seraph of the End: Krul's Tale of Raising a Child

Humans are raised as livestock to provide blood, and their living conditions are terrible. Vampires feed them scraps and other garbage, with no guarantee of safety. Vampires can kill humans whenever they please, and vampires of the Progenitor class can slaughter them en masse. The entire world is ruled by vampires. Yet one vampire is an outlier, and actually adopts a human. P.S. The story differs somewhat from the original: Krul knows nothing about the Seraph of the End plan or her brother, Mahiru never became a demon, and Cursed Gear was never invented in this world.