Watch Mahou Shoujo Lyrical Nanoha

Mahou Shoujo Lyrical Nanoha is about the story of a young girl named Takamachi Nanoha, who suddenly begins hearing crying voices of a talking ferret telepathically in her mind. She then meets the ferret whose name is Yuuno, who is a mage from another planet who had mistakenly sprinkled Jewel Seeds, which are highly dangerous throughout the planet. Unfortunately, without these seeds, Yuuno is unable to transform into his human form, so he asks Nanoha to help him complete this task. In order for Nanoha to assist him, Yuuno gives her a red jewel which instantly transforms her into a magical girl so she can use her magical power to defeat the monsters that stand in their way.