In this fanfiction, they could have an adventure where they explore an uncharted island. The island is full of strange creatures and ancient ruins. Naruto would be cautious and use his ninja skills to scout the area, while Natsu would be more eager to explore and find treasures. They'd end up uncovering a mystery about their own pasts that was hidden on the island, and this discovery would strengthen their bond as brothers and give them new powers to face future challenges.
Maybe they embark on a journey to save their respective worlds from a common threat. A powerful demon or an evil wizard is trying to destroy both the Naruto universe and the Fairy Tail world. Naruto and Natsu would travel across different dimensions, gathering allies from both worlds. Naruto would use his Rasengan and Natsu his Fire Dragon's Roar to fight off hordes of minions while they search for a way to stop the main villain.
The plot could involve them discovering their brotherhood. Maybe they start off in different worlds and then some magical or mysterious event brings them together. They then realize they are brothers and start to explore their combined powers to fight against a common enemy.
It could work if there was a shared backstory created for them. Perhaps they both have a common ancestor or some ancient power that links them. Naruto's strong sense of loyalty and protection could be extended to Natsu as his younger brother. He could teach Natsu some of his ninja values like never giving up and the importance of teamwork. Natsu, in turn, could show Naruto the more carefree and adventurous side of the Fairy Tail world.
In this fanfiction, it could start with Naruto feeling a strange connection to Natsu. As they meet, they discover their shared blood relation. Then, they embark on a journey to find out more about their family's past. Along the way, they encounter various challenges like facing off against enemies who are after their unique powers. They rely on each other's strengths, Naruto's strategic thinking and Natsu's brute force and magic, to survive and grow closer as brothers.
They could have adventures where they explore different dimensions. Naruto's ability to travel through his world could be combined with Ben's inter - galactic travels using the Omnitrix. They might end up in a dimension full of strange creatures and have to fight their way out together.
Yes, there are likely some fanfictions out there with this concept. The 'Naruto' and 'Fairy Tail' (where Natsu is from) fandoms are both quite large, and fans often like to create crossovers that connect different universes in interesting ways.
They could have an adventure where they have to stop an evil wizard who is stealing chakra and magic energy. Naruto uses his ninja skills and Lucy uses her celestial spirit magic to track down the wizard and defeat him.
Natsu could inherit the ability to use chakra. This would give him an extra edge in combat, allowing him to perform jutsus like Naruto. Maybe he could even learn the Rasengan, which he could combine with his fire magic for a super - powerful attack.
If Naruto is Esdeath's brother in fanfiction, they could embark on adventures across different dimensions. Since Naruto has experience with his own world and Esdeath with hers, they could explore new lands together. They might encounter strange creatures and powerful enemies. Along the way, they could learn from each other's fighting styles and abilities, Naruto teaching Esdeath about chakra and she teaching him about her own brand of combat techniques. And they could also be on a quest to reunite their fragmented family or uncover a long - hidden family secret that has the power to change their worlds.
Some fanfictions might show them having adventures within the village itself. For instance, they could be on a mission to solve a mystery that's been plaguing the village, like a series of strange disappearances. Naruto would use his detective skills, which he's developed over the years, and his siblings would learn from him as they go along.
Well, it could be about Naruto somehow ending up in the Fairy Tail world and meeting Natsu. Maybe they team up to fight a common enemy. Naruto's jutsus and Natsu's dragon slayer magic could combine in interesting ways during battles.