Third grader Takamachi Nanoha stumbled upon an injured talking ferret after hearing his telepathic cries for help. The ferret turned out to be Yuuno, an archeologist and mage from another world who had accidentally scattered the dangerous Jewel Seeds throughout Earth. Without the strength to collect the Jewel Seeds, Yuuno had resumed a ferret form and needed someone else to take on the task for him. He gave a red jewel to Nanoha explaining to her with this she could transform and use magic to combat the monsters that threatened them due to the Jewel Seeds. But the monsters are the least of their worries, as Yuuno and Nanoha are not the only ones out to collect the Jewel Seeds.