Maybe Naruto, being a devil, has some special powers that are needed to save the Fairy Tail guild from a great threat. Erza is initially skeptical of him, but as they work together, they develop a bond. Along the way, there could be flashbacks to Naruto's past in his own world and how he became a devil, which would add depth to the story.
I'm not sure specifically which ones are great for this particular crossover. You could try searching on fanfiction websites like Archive of Our Own or FanFiction.net. Just use the relevant tags like 'Fairy Tail', 'Naruto', 'Devil', and 'Erza' to narrow down the search.
Erza might be shocked. After all, Naruto is an important part of her life in the fanfiction. She could initially try to convince him to stay, using her own experiences in Fairy Tail to persuade him.
One great 'Naruto' fanfiction is 'A New Path' which explores an alternate story for Naruto. For 'Fairy Tail' and Erza, 'Erza's Redemption' is quite interesting. It delves into her past and how she overcomes certain traumas. Another 'Naruto' fanfic could be 'The Hidden Power' which gives Naruto some unique abilities not seen in the original. These fanfictions are great because they expand on the original universes and characters in creative ways.
Well, Naruto is the type to make friends quickly and is always looking for a good fight. Erza, on the other hand, is more reserved in her relationships. However, when they are in combat, they would both show their tenacity. Naruto would crack jokes during battles which might make Erza roll her eyes at first, but then she'd start to enjoy his light - heartedness. They would balance each other out, with Naruto bringing out Erza's more fun side and Erza teaching Naruto more about self - control.
Maybe they could be rivals at first. Erza is highly competitive, and Naruto is always looking to prove himself. Their initial rivalry could turn into respect as they see each other's skills in combat. For example, Naruto might be impressed by Erza's ability to change armors and use different types of magic, while Erza could admire Naruto's never - give - up attitude and his powerful jutsu.
Another fanfiction concept could be that Erza somehow ends up in the Naruto universe. She might join Naruto's team for a mission. Erza's strong sense of justice and her powerful magic would be really interesting to see in the context of Naruto's world. For example, she could use her armor magic to help Naruto and his friends in a battle against a powerful enemy.
A possible plot is that Naruto is mistaken for a powerful wizard in the Fairy Tail world. Erza initially doubts him but as they get into battles together, she realizes his strength. They have to work together to stop a ancient evil that is awakening. Along the way, Naruto's positive attitude starts to change the way the Fairy Tail guild members view things, and Erza becomes more open - minded due to Naruto's influence.
The idea of two versions of the same character in a relationship is really fascinating. It allows for a deep exploration of the character's personality. Writers can play with the similarities and differences, like how they might react to the same situation differently. It also gives room for some really unique and emotional storylines, such as self - discovery through the other. In many fanfictions, they might start as rivals but then gradually develop a deeper connection, which is very engaging to read.
Well, without reading the actual fanfiction, it's hard to say exactly. But generally, it could be that the author wanted to combine the popular Naruto character with the magical and often wild world of Fairy Tail and added a devilish twist to it. Maybe Naruto is a devil in this fanfic, which would change his personality and abilities completely, and the story could be about how he navigates the Fairy Tail world with his new identity.