Dragon Sword and Wind Child(1988)

The God of Light and the Goddess of Darkness have waged a ruthless war across the land of Toyoashihara for generations. But for fifteen-year-old Saya, the war is far away—until the day she discovers that she is the reincarnation of the Water Maiden and a princess of the Children of the Dark.

Raised to love the Light and detest the Dark, Saya must come to terms with her heritage even as the Light and Dark both seek to claim her, for she is the only mortal who an awaken the legendary Dragon Sword, the weapon destined to bring an end to he war. Can Saya make the choice between the Light and Dark, or is she doomed—like all the Water Maidens who came before her...?

(Source: Haikasoru)