Secretly, Naga is actually Princess Gracia Ul Naga Seiryuun, the eldest daughter of Crown Prince Philionel El Di Seiryuun who is next in line of the throne of the Holy Kingdom of Seiryuun; one of the largest and perhaps the most powerful kingdom in existence. Seiryuun is also considered the "Capital of White Magic" and is renowned for it's legendary mages. Gracia's mother was murdered before her eyes by an assassin when she was a young girl and she in turn killed him with a magical spell and as a result, Gracia developed an extreme phobia about blood; often fainting or swooning when she sees it.
Afterwards, Gracia abandoned her royal heritage and became a wandering sorceress and adventurer as Naga the White Serpent. Along the way, Naga encountered a young sorceress known as Lina Inverse and promptly decided that she was an adequate sidekick and traveling companion. Lina considers her a nuisance and pest; and often tries to ditch her.
Lina is actually unaware of the fact that her frequent companion; Amelia Wil Tesla Seiryuun is actually the younger sister of Naga or that Naga is actually related to the Seiryuun Royal Family, whom she has encountered on several different occasions. In fact, a recurring gag in the series is that Naga and Ameila always miss seeing one another.