Ciel

The demon monarch Lu emerges in Elrios as a small child after using up all her mana to escape the realm of demons. Due to her servant's betrayal, she has lost all her power and possessions. A hitman named Ciel finds Lu in her weak state and takes her in. Her name is all she remembers. Before long, assassins from the demon world come for Lu, and Ciel gives his life to protect her. Just then, Lu remembers everything. A mystical contract allows her to revive Ciel as a half-demon, and he is bound to serve her in return. Now, with Ciel's help, Lu sets out to take everything back. Together, they ...