1979’s The Leopard Mask is the first volume in Kaoru Kurimoto’s one hundred volume plus (!) sword-and-sorcery Guin Saga. The 2003 English translation is by Alexander O. Smith and Elye J. Alexander.
The kingdom of Parros was peaceful and prosperous; its nobility was elegant and pious. It was a jewel of a kingdom. All the neighbouring Archduchy of Mongaul had going for it was a large army. This allowed Mongaul to crush its elegant neighbour.
The invading Mongaul attack managed to kill all but two members of Parros’ royal family. Twins Rinda and Remus — the Pearls of Parros — escape to the Roodwood. It’s a tossup whether Mongaul’s soldiers will capture the two teens before the Roodwood’s monsters eat them.