Amitie and Kyrie are sisters living on the dying planet Eltria; a harsh world that their scientist parents have been working for years trying to save. But the poisonous environment is slowly killing their father, and his dream of restoring the planet is dying with him. Kyrie runs away and travels to Earth to steal the power she believes will save her family and her home: Hayate's Book of Darkness! Amitie follows in hot pursuit, knowing her desperate sister is willing to go to dangerous lengths to accomplish her goal. Can Nanoha, Fate, and Hayate defend Earth from this new threat?