Well, in a Naruto, Shinju and Fairy Tail fanfiction, the worlds could collide in many ways. For example, perhaps a powerful magic from Fairy Tail accidentally opens a portal to the Naruto universe where the Shinju exists. The characters from Fairy Tail, with their unique magical abilities, might be intrigued by the chakra system in Naruto. And the presence of the Shinju could be a huge draw as it's such a powerful and mysterious entity. They could either form alliances or end up in conflicts due to misunderstandings about each other's powers and motives.
A possible plot could be that the Shinju starts to corrupt the magic in the Fairy Tail world. The Fairy Tail wizards notice strange changes in their spells and realize it's related to the Shinju. They seek help from the Naruto universe, and together with Naruto and his friends, they embark on a journey to find the source of the corruption within the Shinju. Another plot could be a tournament - style story where characters from Naruto, those related to the Shinju, and Fairy Tail mages compete against each other in a series of challenges that combine magic, chakra, and the power of the Shinju.
In that fanfiction, it might be designed that way. Naruto has incredible powers in his own series, like his various jutsu. If translated into the Fairy Tail world in fanfiction, his skills could potentially make him very powerful. But it also depends on how the author of the fanfiction interprets and balances the power systems of both universes.
The Sharingan in such a fanfiction could be used as a tool for a Fairy Tail character to gain an edge in their battles. They might initially struggle to control it, but as they learn more about it, they become a formidable force. For instance, they could use the Sharingan's genjutsu abilities to deceive opponents in the Fairy Tail battles.
Well, one possible consequence could be that he gains some sort of super - power. Since the Shinju is a very powerful and mysterious entity in the Naruto universe, consuming it might endow Naruto with abilities beyond his normal limits. Maybe he could gain control over new types of chakra or even have a better understanding of the origin of all things in the ninja world.
He might be desperate. Maybe there is a great threat to the ninja world that can only be defeated by the power of the Shinju. Naruto, being the hero he is, decides to take the risk of eating it in order to gain the power needed to save everyone.
In the Fairy Tail world, Naruto would bring his unique ninja abilities. For example, his shadow clone jutsu could be used in creative ways during battles or to perform tasks. He would likely befriend Natsu because they both have a passion for fighting and protecting their friends. Naruto could also introduce new combat styles to the Fairy Tail guild, which might change the way they approach battles.
Well, Naruto would probably gain some really unique magical abilities. Fairy Tail mages are known for their diverse magic, and Naruto could combine his chakra skills with something like Fire Magic or Celestial Magic. He might become even more powerful in combat, with new ways to attack and defend.
Well, Naruto's ninjutsu skills would be quite a novelty in the Fairy Tail world. His shadow clone jutsu could be used in some really creative ways during battles, like overwhelming opponents with a large number of clones. Team 7 as a whole would bring a different dynamic. Sasuke's sharingan could give them an edge in detecting magic and illusions. Sakura, with her medical skills, could be a great asset in treating wounded mages. And Kakashi, with his experience and wide range of jutsu, would be like a mentor figure to the Fairy Tail members, teaching them new strategies.
Well, if Naruto was in the S - Class of Fairy Tail, his combat skills would be a great addition. Naruto's ability to use shadow clones could be used for various strategic purposes during Fairy Tail's missions. He could send clones to scout ahead or create distractions in battles against dark guilds.