Gray could be the main character as well. His cool and collected demeanor could contrast with the chaos of the mental hospital. He might be sent there on an undercover mission to find a dark wizard who is hiding among the patients or staff. His ice - make magic could come in handy when dealing with any threats or obstacles within the hospital.
Lucy might also be a suitable main character. Her kind heart would lead her to try and help the other patients. She could use her celestial magic in unique ways to communicate with those who seem lost in their own minds. Maybe she gets trapped in the mental hospital while looking for a lost Celestial Spirit item and has to find a way to escape while also helping those in need.
Sakura could also be a main character. As a medic - ninja, she might be involved in Naruto's treatment in the mental hospital. She could bring her own knowledge and her relationship with Naruto into play, adding depth to the story.
Perhaps a group of Fairy Tail wizards visit the mental hospital as part of a community service mission. They discover that some of the patients are not actually crazy but are under the influence of a curse or a forgotten magic spell. The wizards then have to find a way to break the spell without causing chaos in the hospital, all while dealing with the hospital's strict rules and the skepticism of the staff.
Gray could be the main character in a harem fanfiction. His cool exterior and his ability to use ice magic in such a unique way make him stand out. He has a bit of a rivalry with Natsu which could add an interesting dynamic to the harem. Characters might be attracted to his brooding nature and his underlying loyalty to his friends and the guild.
It could be a new character, like a street - smart orphan who has learned to steal to survive. This character sees Fairy Tail as a source of wealth at first but then discovers there's more to the guild than just gold and jewels. Another option is an ex - member of a rival guild who turns to thievery after being exiled and decides to target Fairy Tail for revenge. Or it could be a magical creature, like a mischievous imp with the power of invisibility that steals from Fairy Tail just for fun.
Lucy would also be a great main character. Since she has a collection of celestial spirits, adding a genie to her story would be fascinating. She could struggle with whether to use the genie's wishes or rely on her spirits, and the genie might be jealous of her celestial spirits, leading to conflict and character development.
Natsu could be an interesting choice. Imagine if he accidentally caused a great deal of damage during a battle and had to make up for it. He would use his fire - dragon - slayer magic in new ways to help the guild and the people they protect.
Natsu could be a great main character for a Fairy Tail wolf fanfiction. Picture Natsu befriending a wild wolf in the forest that has some kind of fire - related power. Natsu and the wolf could team up to fight against stronger enemies. They might learn from each other and develop new fighting techniques. Erza could also be a main character. She could find a magical wolf armor that gives her enhanced strength and speed, and she has to master using it while also protecting the wolf that is somehow connected to the armor. Additionally, a mysterious outsider who has the power to control wolves could be the main character, bringing a new and dangerous element to the Fairy Tail world.
Lucy could be a great main character. Since she has a collection of celestial keys, the Rinnegan could give her new ways to interact with her spirits. For example, she might be able to use the Rinnegan to enter the spirit realm directly without using the keys, or enhance the power of her spirits when they are summoned. It would be an interesting twist on her character and her abilities.
It could be an original angel character that you create. This angel could have special powers like the ability to heal any wound or the power to manipulate light in unique ways. They would enter the Fairy Tail world and become the central figure in the story, interacting with all the well - known Fairy Tail characters.
Natsu could be a great main character. He's always hungry and loves food. He could be on a quest to find the ultimate cheeseburger in the Fairy Tail world. Maybe it's hidden in a dangerous dungeon, and he has to battle through all kinds of monsters just to get a taste of it.