Nanoha Takamachi is a 3rd grade elementary school girl. She lives with her parents who run a coffee shop, and her older sister and brother who are in high school and university respectively. Nanoha's regular life changes when she hears a voice calling to her on the way home and ends up rescuing an injured ferret (who is actually a transformed boy called Yūno, an archaeologist from a distant world). She obtains a magical crystal called Raising Heart (レイジングハート, Reijingu Hāto?), and gains magical powers.
After their encounter, Nanoha and Yūno have to collect the twenty-one "Jewel Seeds" (ジュエルシード, Jueru Shīdo?), powerful lost crystals from Yūno's world that grant wishes and are very dangerous when misused. However, Nanoha and Yūno are not the only ones after the Jewel Seeds. So is Fate Testarossa, a foreign girl with sad eyes...
Nanoha Takamachi (高町 なのは, Takamachi Nanoha?)
- This sweet grade three student feels that, though she plays a good supporting role in others' lives, unlike the rest of her family and friends, she has no closest friend to turn to and no direction in her own life. However, when she meets Yūno and discovers her strong aptitude for magic, Nanoha activates the magical crystal, Raising Heart, that Yūno was carrying and wholeheartedly carries out her search for the Jewel Seeds.
Yūno Scrya (ユーノ・スクライア, Yūno Sukuraia?)
- Yūno is a magic-user from Midchilda, and is the same age as Nanoha. Despite his young age, he worked as an archaeologist and discovered a set of ancient and powerful artifacts (the magical term for this is Lost Logia) known as the Jewel Seeds. When the Time-Space Administration Bureau lost the Jewel Seeds, Yūno went to Earth to track them down; whilst fleeing from monsters, he was injured and transformed himself into a ferret. He is mistaken as Nanoha's familiar, though his true form is that of a regular human.
Fate Testarossa (フェイト・テスタロッサ, Feito Tesutarossa?)
- Voiced by: Nana Mizuki (Japanese), Jennifer Alyx (English)
- Abused by her ruthless mother, Fate regardless remains blindly and unquestioningly loyal to Precia and carries out her search for the Jewel Seeds. However, as Nanoha persists to try to learn her motivation and become her friend, Fate is faced with a shocking truth from everyone around her and must decide what to do with it.
Arf (アルフ, Arufu?)
- Fate's outspoken dog-woman familiar. Her distaste of Precia is mutual, but she cannot do anything to protect Fate from her mother. Arf instead takes out her anger on her enemies. She is very kind to Fate and rather protective of her.
Precia Testarossa (プレシア・テスタロッサ, Pureshia Tesutarossa?)
- Voiced by: Rei Igarashi (Japanese), Julie Rei Goldstein (English)
- Precia is a mage residing in the Garden of Time. She went insane when her daughter Alicia died. She instructs her daughter Fate to find the Jewel Seeds and beats her ruthlessly when she does not do enough to satisfy her. Precia desperately wants the Jewel Seeds to revive Alicia, to the point that she will not hesitate to remove any obstacles. She was kind and stable once upon a time, but any trace of that is long gone.
フェイト・テスタロッサ, Feito Tesutarossa