Tensei Shita Daiseijo wa, Seijo de Aru Koto wo Hitakakusu - ZERO ~The Great Saint of Remembrance~

It's three hundred years before Fia and her friends' adventures in Náv, and Princess Serafina, the blind second princess of the land, lives hidden away in the forest. With only the forest spirits and her cousin, the young knight captain Sirius Ulysses, to keep her company, Serafina leads a peaceful life. But one day, an incident causes mysterious powers to awaken within her, and Serafina takes her first steps on the path that will ultimately lead her to becoming the one and only Great Saint!