The Guin Saga Manga: The Seven Magi

When the militaristic duchy of Mongaul overruns its elegant neighbor, the kingdom of Parros, the only survivors of the lost kingdom's royalty are the young, platinum blond twins Rinda and Remus, and as the twins hide out in a forest in the wild borderlands, they are saved from a Mongaul patrol by a creature with a man's body and a leopard's head--a creature known as Guin.