Nina is a girl in middle school with a little brother and a single mom who barely has enough time to spend with her. Put down at school by nasty cliques, Nina's life is not much fun. All this changes when a magical fairy named Sybil turns up in Nina's backpack! Sybil and Nina have a blast giving Nina's tormentors a taste of their own medicine. There's only one problem: demons from the magical world that Sybil comes from have followed her to our dimension, and they're out to cause some damage of their own!

Nina loves having her backpack fairy Sybil around! Nina is the only person who can see or hear Sybil and the two have formed a special bond. But when Sybil unexpectedly disappears, a new fairy named Amanite shows up to take her place. Amanite brings Nina to a magical underwater world, where Nina is magically transformed into a tiny mermaid! But then things go horribly wrong when sea monsters decide that Nina look mighty delicious! Where’s Sybil when Nina really needs her?

Having a fairy friend can be fun, but it’s not easy. When Nina first met the fairy Sybil and her companion Pandigole, she had no idea the fate of the world would end up resting in her hands. After her defeat in SYBIL THE BACKPACK FAIRY #2, the black fairy Amanite has teamed up with the King of Evil, Aithor, planning to destroy the “trees of life” that are found throughout the world of the Fairies. If these trees are destroyed, not only will the fairy world fall, but the world of humans, as well. In response, the King and Queen of the fairies charge Sybil and Nina with the task of stopping Aithor and Amanite, as Nina gets closer to discovering the truth behind a mysterious prophecy that seems to foretell her future.