Takamachi Nanoha is a 3rd grade elementary school girl. One day she hears a voice belonging Yuuno Scraia, a mage from another world who came to this world to collect and seal the "Jewel Seeds". Yuuno was injured during a battle and had to take the form of a ferret. When Nanoha finds him he tells her about his mission and gives her a special device to help her use her powers. Nanoha decides to help Yuuno to collect the seeds and they go on adventures together while collecting the Jewel Seeds.