Vampire Doctor

The protagonist, who lost her mother when she was a child, became a detective to investigate the identity of her mother's killer. While looking into a different case, she gets herself into trouble and is saved by a vampire called Doctor Al. In exchange for her blood, Al helps her search for the criminal who killed her mother. However... every time Al sucks her blood, "Al's past" attacks her, sensually. But to reach the truth she must give up her own blood. Can you reach a happy conclusion, or will it be...