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.
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.
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.
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.
I really like 'Erza's New Journey in Naruto'. In this fanfic, Erza somehow gets transported to the Naruto world. The story shows how she adapts to the new environment, with all the ninjutsu and different cultures. It's fascinating to see her interact with Naruto and his friends. Also, 'Fusion of Powers' is a good read. It's about a scenario where the powers of Naruto characters and Erza's magic start to blend, creating some unexpected and exciting situations.
One possibility is that Naruto leaving Fairy Tail could lead to a rift between him and Erza at first. However, as time passes, they might realize that their friendship is stronger than the guild. Naruto could bring his ninja ideology to other parts of the world, influencing the way people think about power and teamwork. He might also find himself in situations where he has to use his wits more than his strength, as he won't have the support of Fairy Tail. This could be a turning point for his character development, making him more self - reliant.
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.
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.
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 common theme is the adventure - based stories. Writers send Erza and Naruto characters on quests together. It could be to find a powerful artifact that has significance in both worlds. In these fanfics, they face various obstacles and enemies along the way. Also, the theme of friendship is prevalent. It shows how Erza forms deep bonds with the Naruto characters, like how she might become great friends with Sakura, sharing their experiences as strong female characters in different but equally dangerous worlds.