Well, a cool fanfiction could be about a chain - like weapon inspired by Chains in a Naruto - Fairy Tail crossover. Maybe a character from Fairy Tail creates a special chain weapon using their magic, but it also has the chakra - like properties from Naruto. This weapon could have unique abilities that help the characters in their adventures. Also, a story where the main character is a descendant of characters from all three series and has to discover their heritage while facing various challenges would be interesting.
A possible fanfiction concept could involve a training arc. Imagine a group of characters from Naruto and Fairy Tail are sent to the Chains world for a special training. In this world, they have to adapt to new rules and powers. The Naruto characters might learn about different types of chains and how to use them in combat, similar to how they use ninja tools. The Fairy Tail mages could infuse their magic into the chains, creating new and powerful attacks. This training arc could lead to stronger bonds between the characters and new abilities that they bring back to their respective worlds.
One idea could be a crossover where characters from Naruto and Fairy Tail end up in the world of Chains. For example, Naruto's ninjutsu skills could be combined with Fairy Tail's magic in the strange and dangerous Chains world. Another idea is a story about a character who has the powers of all three universes and has to use them to save the multiverse from a great evil.
One idea could be a crossover where Naruto characters learn magic from Fairy Tail. For example, Naruto might learn fire magic and combine it with his Rasengan. Another idea is that the guilds in Fairy Tail and the villages in Naruto have to team up to fight a common enemy, like an ancient dark force. And perhaps some of the Fairy Tail wizards could teach the ninja in Naruto about the power of friendship and how it can enhance their abilities.
One idea could be exploring the different types of chains in the Naruto universe. For example, chains that are made from chakra and have special abilities like restraining powerful foes or sealing jutsu. Another idea is to create a story where a new character has a unique chain - based fighting style that surprises everyone in the Hidden Leaf Village.
One idea could be a crossover where Naruto and Lucy team up to fight a common enemy. Maybe a powerful dark mage from Fairy Tail's world has somehow made its way into the Naruto universe and is causing chaos. Naruto's ninja skills combined with Lucy's celestial spirit magic would make for an exciting battle.
One idea could be a crossover where a character from Fairy Tail somehow gains the Kamui ability. They could use it in battles against dark guilds in the Fairy Tail world, opening portals to surprise enemies or escape dangerous situations.
One idea could be to have Naruto characters learn magic from Fairy Tail. For example, Naruto could learn Fire Magic, which would be an interesting twist on his own Fire - Style jutsu. It would also be cool to see how Fairy Tail characters react to the ninja world's politics and strict hierarchies.
One idea could be a crossover where the magic from Fairy Tail combines with the ninja skills in Naruto. For example, Naruto characters could learn magic and Fairy Tail mages could learn ninja techniques. In the harem aspect, the main character, say Naruto, could have female characters from both series attracted to him because of his newfound powers and his unique personality traits.
One interesting idea could be exploring the origin of the Adamantine Chains in more depth. Maybe they have a connection to an ancient clan that was long forgotten. Another idea might be a story where the chains are used in a unique way to save the Hidden Leaf Village from a powerful enemy.
You could do a time - travel fanfiction. Have a character go back in time to when the Fairy Tail guild was first founded and see how they interact with the founders. Or, write a story where the characters swap powers. So, Erza would have Lucy's celestial magic and Lucy would have to use Erza's requip magic. This would lead to a lot of comical and also challenging situations for them. Also, you could write a fanfic about the guild taking on a mission in a completely new and strange land, filled with magic they've never seen before.
One idea could be exploring an alternate universe where the main characters have different magic abilities. For example, Natsu could have ice - based magic instead of fire. Another idea is to focus on the backstories of the minor characters in more depth, like how they came to join Fairy Tail. A third idea would be to create a time - travel fanfiction where characters go back in time to change a significant event in the Fairy Tail world.
One idea could be exploring an alternate universe where the main characters have different magic powers. For example, Natsu could have ice - based magic instead of fire. Another idea is to focus on a backstory for a minor character, like how they came to join the guild. Maybe a story about a character's journey to find a long - lost magical artifact that has a connection to Fairy Tail's history.