They could have adventures where they combine their skills. Naruto could use his ninja techniques like shadow clones, and Erza could use her different armors and magic. For example, they might fight against a powerful enemy that is a threat to both their worlds. Naruto's clones could distract the enemy while Erza changes into her strongest armor to deliver a powerful blow.
One adventure could be exploring different dimensions. Since Naruto is from his ninja world and Erza from Fairy Tail, they could use their combined knowledge and abilities to travel through various dimensions. They might encounter strange creatures and new forms of magic and jutsu along the way. And of course, they would be protecting each other as siblings should. Maybe they would find a way to bring peace to all the worlds they visit.
Naruto might gain the ability to use magic weapons like Erza. Since he's a quick learner, he could master the use of different magical swords or armors. He could infuse his chakra into these weapons to make them even more powerful. For instance, a sword that can cut through any material when combined with his chakra and also has the ability to cast magic spells.
They could start by meeting in a strange, in - between world. Naruto is intrigued by Erza's armor and Mirajane's different forms. They soon realize they have a common goal, which is to find a way back to their own worlds. As they journey, they share stories of their past adventures, with Naruto talking about his battles in the Hidden Leaf Village and Erza and Mirajane sharing tales from Fairy Tail.
One common theme is the idea of family. Since Naruto and Erza are in a brother - sister relationship in these fanfics, the concept of building a new family, loyalty, and protecting each other is often explored.
One way this could work is if there was a shared ancestry that was hidden or lost over time. Perhaps there was an ancient clan that had members in both the Naruto world and the Fairy Tail world. Through some convoluted plot device in the fanfic, Naruto and Erza could be discovered to be part of this long - forgotten clan, thus making them siblings.
For Naruto, his development could focus on how he adapts to the magic - filled world of Fairy Tail. He might start to question his own ninja abilities and learn to incorporate magic into his fighting style. For example, he could learn to use chakra in new ways inspired by magic. Erza, on the other hand, could develop by learning about Naruto's strong sense of loyalty and how it differs from the loyalty within the guild. This could make her re - evaluate her relationships and her role in the guild.
Well, Naruto might bring his ninja skills to Erza's world. He could use his shadow clone jutsu to help Erza in battles. Maybe he'd be a bit of a troublemaker at first, not fully understanding the rules of Erza's guild. But over time, he'd grow to respect and adapt to it, using his unique abilities to support Erza and her friends.
Well, in this fanfiction concept, it could work in terms of Naruto's protective nature. Naruto is known for his loyalty and his will to protect those he cares about. If he were Erza's older brother, he would surely use his skills and abilities to keep her safe. He could teach her some of his ninja techniques, which would be really cool to see combined with Erza's own combat skills. Also, Naruto's positive attitude could influence Erza in a different way, making her more open and perhaps less brooding at times.
He could be a very powerful mage, perhaps even more powerful than Erza in some aspects. For example, he might have a unique form of magic that is rare in the Fairy Tail universe, like the ability to control time on a small scale. This would make him a valuable asset in battles and also a target for enemies who want to use his power for their own evil purposes.
Yes, there are likely some fanfictions out there with such a concept. Fanfiction writers often come up with creative crossovers like this. However, the quality and nature of such fanfictions can vary greatly. Some might focus on how Naruto's ninja skills could influence Erza's world in Fairy Tail, while others could explore the family dynamic between them in an interesting way.
She could influence his sense of loyalty. Erza is extremely loyal to her guild, and she would instill in Naruto an even deeper loyalty to his village and his friends. He might become more protective and dedicated to those he cares about. Also, Erza's own story of struggle and growth could inspire Naruto to keep pushing himself, even when things seem difficult.