Guin Saga

In a single day and night of fierce fighting, the Archduchy of Mongaul has overrun its elegant neighbor, Parros. The lost priest kingdom's surviving royalty, the young twins Rinda and Remus, hide in a forest in the forbidding wild marshes. There they are saved by a mysterious creature with a man's body and a leopard's head, who has emerged from a deep sleep and remembers only his name. Guin.

(Source: Vertical Inc.)