Perhaps in the fanfiction, Naruto and Jellal are actually long - lost brothers from different dimensions. Naruto, with his determination and will to protect, tries to find a way to free Jellal from any dark influences in his world. He uses his ninja knowledge and chakra abilities in place of magic to face the enemies in Jellal's world. The plot could revolve around their journey to uncover the truth about their relationship and save their respective worlds from a common threat.
In this fanfiction, it could start with Naruto waking up in Jellal's body. He has no idea how he got there. As he tries to figure out what's going on, he discovers that Jellal's world is in chaos. Using Naruto's indomitable spirit and his own unique take on Jellal's powers (if he has access to them), he starts to rally the people around him. He tries to bring peace to the land, all while trying to find a way back to his own world. Along the way, he might make new friends and enemies, and his ninja values could have a profound impact on the people of Jellal's world.
One possible plot could be that Naruto somehow gets transported to the world where Jellal is. He has to adapt to the new magic - based environment using his ninja skills. Maybe he is mistaken for Jellal at first and has to deal with the consequences of that identity mix - up.
The plot could involve Naruto being haunted by Hashirama's spirit. Hashirama's spirit appears to Naruto during difficult times in his life, like when he's facing tough opponents or making important decisions. Hashirama gives Naruto advice based on his own experiences. As Naruto continues to interact with Hashirama's spirit, he becomes more and more of a 'fan' and starts to model his behavior and beliefs after Hashirama. This could lead to Naruto bringing about a new era of peace in the ninja world, inspired by Hashirama's vision.
One possible plot is that Naruto and Lobo are merged into one being. This new entity has the powers of both Naruto and Lobo. It then goes on a journey to find a way to separate them again while facing various challenges along the way. The story could involve battles against powerful foes who are interested in this new and unique power. There could also be a sub - plot about how Naruto's friends in his original world are trying to find a way to bring him back.
One possible plot could be that Naruto is somehow magically transformed into a Spectre - like being. He then has to figure out how to use his new powers while still holding onto his ninja identity. Maybe he has to fight against an evil force that is threatening both the Naruto world and the Spectre world.
Maybe the Naruto character gets transported to the Pokemon world and somehow ends up taking care of a group of Pokemon as if they were his children. He could use his combat skills to protect them from danger.
Perhaps the plot could center around Naruto having to fight against villains who are embodiments of the seven deadly sins. Each villain would have powers related to their respective sin. Naruto would then have to use his ninja skills and his own sense of justice to defeat them one by one, learning about the nature of these sins along the way.
It could be about a mission that Naruto and his team go on and it has to be completed by dawn. Maybe there are some dangerous enemies they have to face, and as the night progresses, the tension builds until it all comes to a head at dawn.
The plot could involve Naruto being possessed by the essence of the Void Lord. This changes his personality and makes him more of an anti - hero at first. His friends, like Sasuke and Sakura, try to bring him back to his normal self while Naruto struggles with the dark urges and new abilities that come with being the Void Lord. Meanwhile, there could be a new villain who wants to use Naruto's new state for their own evil purposes.
It's really hard to say without actually seeing such a fanfiction. But perhaps it could be related to Naruto getting into some sort of difficult situation, like a magical or physical knot that he has to overcome, and the story could revolve around his journey to untie it, both literally and metaphorically.
One possible plot could be that Naruto discovers his relation to Makarov later in his life. He then travels to the Fairy Tail world to learn more about his heritage. Along the way, he might face challenges from both Naruto's world enemies who follow him and Fairy Tail enemies who don't trust this new stranger. He has to use his ninja skills and the newfound magic abilities he might inherit from Makarov to prove himself and protect his new family.
Perhaps in the fanfiction, All Might visits the Naruto universe. Naruto is intrigued by his power and starts to train under him. Together, they face a new threat that combines the dark forces of the Naruto world and some villains from My Hero Academia. The plot could revolve around how they use their combined skills and knowledge to defeat this new enemy.