Nanoha Takamachi has a very ordinary life as a third grader at Seishou Elementary School. She lives with her parents who run a cafe, and her older brother and sister. On the way home from school one day, she and her friends Arisa and Suzuka find an injured ferret in the park. This ferret is actually Yuuno, a young mage from another world. To save him from a mysterious black shadow, Nanoha takes up the magical staff, "Raising Heart."