Naruto could save Fairy Tail in fanfiction through his strong will and never - give - up attitude. He has faced numerous challenges in his own world and emerged victorious. In the Fairy Tail universe, he could inspire the members of the guild to keep fighting even when all seems lost. He might teach them some of his ninja techniques which could give them an edge in battles. His experience in dealing with powerful and dangerous opponents would be invaluable in protecting Fairy Tail.
Mirajane could be a key character in a fanfiction where the worlds of Naruto and Fairy Tail are merging. Her strong magical powers would make her a valuable ally. In this merged world, she could help Naruto train to control new types of energy that are a combination of chakra and magic. She could also share Fairy Tail's sense of community and friendship with Naruto and his friends, which would strengthen their bonds and make them more united against any threats.
It could work by making Naruto a more mysterious and brooding character. In Fairy Tail, there are many characters with different personalities. An emotionless Naruto would stand out. He might be more focused on achieving his goals without being distracted by emotions. For example, he could be on a mission to find a way back to his own world and his lack of emotion helps him stay determined.
One way could be through a magical portal. Maybe a powerful mage in Fairy Tail accidentally creates a portal that links to the Naruto universe and Madara somehow gets sucked through it. Then he could use his powerful jutsu in the Fairy Tail world, creating all sorts of chaos and new storylines.
In a Naruto - Fairy Tail fanfiction where Naruto is a brother figure, he might bring a whole new dynamic. He could teach the Fairy Tail guild members some of his ninja training techniques. For example, how to better endure pain or how to focus their energy more effectively. Also, his backstory of being an outcast in his own village at first could make him relate to some of the Fairy Tail characters who have had difficult pasts.
Perhaps it's a matter of a powerful enemy from Fairy Tail's lore recognizing Naruto as a significant threat and using a very underhanded or extremely powerful attack on him. Since Naruto might not be fully aware of all the rules and powers in the Fairy Tail world, he could be caught off - guard. And in fanfiction, the writer might want to create a very dramatic and unexpected death for the sake of a unique story, so they come up with a scenario where Naruto dies in the Fairy Tail world.
In fanfiction, Naruto could become the founder of Fairy Tail by having his unique ninja skills and values influence the creation of the guild. Maybe he travels to the Fairy Tail world and decides to gather like - minded mages. His leadership skills, learned from being a ninja, would help him in setting up the guild's rules and training methods.
Well, it could be that a character from Fairy Tail somehow travels to the Naruto world and acquires the Rinnegan. Then, when they return to their own world, they have to adapt it to the magic - based system. They might find that the Rinnegan's abilities interact strangely with their own magic, creating new and unexpected effects.
Lucy could save everyone by making a great sacrifice. Maybe she gives up her magic power temporarily or even permanently to stop an evil force. In fanfiction, this could be something really emotional. She might be the only one who can access a certain magical item or place because of her Celestial Spirit keys. By using this advantage, she gets to the root of the problem and saves the day.
In some fanfictions, Natsu might save Lisanna from a powerful dark wizard. He could use his Fire Dragon Slayer magic to overpower the enemy and rescue her.
In some fanfictions, Lucy might use her Celestial Spirit magic. For example, she could summon a powerful spirit like Leo to help fight off whatever is threatening Natsu. The spirit could provide a distraction or directly combat the enemy while Lucy tries to reach Natsu and get him to safety.