Takamachi Nanoha is a 3rd grader elementary school girl. She lives with her parents who run a coffee shop, and her older sister and brother who are students. She was a normal girl until she met a boy that came from another world named Yuuno Scrya. She happens to obtain a magical power from him which she has then to use to recollect "Jewel Seeds". They are from the other world, and are scattered around Earth.
Yuuno Scrya, the boy from the other world, can turn into a small animal, Nanoha herself has a magical wand that is materialized by her will. With these two, she has to recollect the "Jewel Seeds". It will grant one's dream, but it also cause various accidents at times.
She becomes friends with the boy from the other world, and spends her life as a magical girl late at night, early in the morning, after school, and on vaction in secret. Around family and friends, she's just anormal girl.
During her adventures more magical girls with the same power as her appear and almost destroy her otherweise peaceful life.
