Bloodlaced (Youkai Bloodlines Book 1)

Asagi, a servant in the house of a feudal lord, discovers that their master is not a man but a blood-drinking youkai. When Asagi is poisoned, their master turns them to save their life, but the cost is high. Now, with both a literal and proverbial monster at the door, Asagi must decide what it means to be human to protect what they love most.