It's a witch AU based off of Halloweentown, Practical Magic, Sabrina the Teenage Witch, Harry Potter, Monster High, and Hocus Pocus.
In a magic realm there exists witches, warlocks, and monsters who have the ability to go into the mortal realm if they choose and can disguise themselves as mortals. However they are forbidden to reveal their existence to mortals or have any romantic relationship with them. Also monsters and witches/warlocks have an on going war with each other over dominance of the magic realm. In the midst of this there lived Irene, Ondina, and Layla three powerful, wealthy, and beautiful witch sisters who in their youth were very close.
However their strong bond fell apart when Ondina the middle daughter fell in love with a mortal man which disgusted her parents. Irene the oldest daughter, much like her parents believed that mortals were worthless creatures and was completely against the relationship. Layla the youngest daughter didn't really mind the relationship but was too afraid to say anything against her parents and oldest sister (Which she would always regret). When Ondina leaves her arranged fiance and marries her mortal lover her family disowns her and everyone the magic realm persecutes her so she goes to live in the mortal realm with her husband. This breaks Layla's heart and although she does marry her chosen fiance, she distances herself from her family shortly after the marriage.
Years pass and during that time each of the sisters have a daughter who each inherited their mother's powers and familiars. Once the girls become teenagers they discover their lineage, befriend each other, and learn magic together.
Erza - Daughter of Irene and the warlock Rung. The most powerful and intelligent of the three cousins however she is prone to being melodramatic. She is very advanced in all traits of magic but has a special power in nature and the earth. Unlike her parents she doesn't have any ill feelings or views toward mortals and isn't afraid to speak her mind about it. She actually visits the mortal realm plenty of times and even ends up developing a crush on a mortal.
Juvia - Daughter of Ondina and her mortal husband Erik. She is more sensitive and empathetic than her other two cousins. Her magic has a special affinity with love and emotions and she posses a siren-like voice however due to growing up in the mortal realm she has trouble controlling her powers and can be a little clumsy with them. She often educates her cousins on how to behave when they visit the mortal realm.
Lucy - Daughter of Layla and the aristocratic warlock Jude. She's the observant and cheerful of the three with a curious fascination in mortals and monsters. Her powers are mostly associated with seeing the future, clairvoyance, fortunes, and zodiacs. Having lived a sheltered life of the wealthy she's a little naive about somethings but she's a fast learner and is willing to listen.
Makarov - An old warlock who along with two of his apprentices were charged with protecting the ambassador of the magic users and the monsters. However when the ambassador was killed he and his apprentices were blamed by the magic council who punished them by having them spend a hundred years as a powerless animal. Makarov was changed into an owl who now serves as Erza's familiar. He's a very wise and patient teacher to Erza who does everything he can to educate her in the ways of magic and sorcery of course he's not above being a little silly sometimes. He is old.
Gajeel - One of Makarov's apprentices who was changed into a black cat. He serves as Juvia's familiar and since she lives in the mortal realm he has to spend most of his time behaving like a regular cat which bothers him. He's very sarcastic, lazy, and acts like he doesn't care but deep down he has a good heart, he's very fond of Juvia and he would do anything for her. Just don't ever call him her pet.
Laxus - Makarov's grandson and another apprentice who was changed into a hare. He serves as Lucy's familiar and he really hates what he's been reduced to. Like Gajeel he acts like he doesn't care too much for position but secretly he does care about the witch he's assigned to watch over. He often advises Lucy against doing anything that involves mortals but she never listens, still he follows her around to make sure she stays out of trouble. Also he hates it when anyone calls him a cute bunny.
Jellal - A mortal who Erza develops a crush on. He secretly returns her feelings but both him and her are very shy about it. However Jellal comes from a family of witch hunters, one of which happens to be a longtime adversary of Erza's mother. He is raised to believe that witches killed his parents so he harbors hatred toward them yet he doesn't know Erza is a witch and she doesn't know that he's a witch hunter.
Gray - Juvia's best friend and a seemingly normal mortal but in actuality he's the son of a werewolf who fell in love with a mortal. He changes into a wolf like beast every night yet has no memory of it and when he's in his wolf form he becomes a completely devoted protector to Juvia. Neither her or him know about each other's non human lineage but they feel a bond with each other. Sometimes he gets canine urges and tendencies. He and Gajeel have a strong dislike toward each other (Gajeel's a cat and Gray is half wolf so yeah)
Natsu - A vampire who likes to tease the girls and mess with them but is actually a good friend. Throughout his life he's been pushed around by witches and warlocks due to his status of being a monster but luckily he's not bitter to their race. He wants peace between monsters and magic users. so he goes out of his way to help the girls when they need him. He has a not so secret crush on Lucy yet she's completely oblivious to his feelings. He drinks blood but it's animal blood and he wears a special ointment that protects him from sunlight.
Brain - Jellal's uncle and a master witch hunter who was once an enemy of Irene. He hates witches and will do anything he can to destroy them. When his brother and sister in-law died, he raised his nephew to believe that witches were responsible and that he should avenge his parents by killing all witches. But he never counted on his nephew falling for a witch.
Jose - A warlock and Ondina's ex fiance who she left for a mortal. He never got over her rejection and later becomes obsessed with trying to marry Juvia due to her resemblance to her mother but a certain werewolf won't allow him to do that.
Seilah - A witch who used to be Layla's best friend until Layla unintentionally bested her in a magic tournament. She felt humiliated and in anger she attempted to use dark magic which led to her being expelled from the witch academy. She blamed Layla for the whole thing and decides to get revenge by somehow stealing all the magic in the realm and destroying Lucy. She does everything she can to feed the hatred between magic users and monsters so she can manipulate them into giving up their powers.