Well, it could change the story in many ways. For one, Naruto would have a huge power boost. He might be able to easily defeat opponents in the Chunin Exams that he would have struggled with before. His new Tenseigan powers could also attract more attention, both good and bad. Maybe some powerful enemies would target him earlier, or some allies would seek him out for his new strength.
Maybe it was a hidden inheritance. There could be some long - lost family connection that no one knew about, and during the Chunin Exams, some event triggered the awakening of the Tenseigan within Naruto.
In such a fanfiction scenario, Naruto would be extremely powerful. He could easily overpower his opponents during the Chunin Exams. The other genin would be in awe or extreme fear. His control over the ten - tails' power would likely be a major plot point, as it's such a vast and dangerous amount of chakra.
In this fanfiction scenario, Naruto and Yugito could have some really interesting interactions during the Chunin Exams. Maybe they start off as rivals, each determined to prove themselves in the exams. Naruto with his unwavering determination and Yugito with her unique skills. They might end up in a match against each other, and through the battle, they gain a newfound respect for one another's abilities.
One idea could be that Naruto forms an unexpected alliance with Anko during the Chunin Exams. Maybe they team up to uncover a hidden plot within the exams that threatens the safety of all the genin. Anko, with her experience, could help Naruto see things from a different perspective and he, in turn, could inspire her with his determination.
One idea could be that female Naruto has unique jutsu in the Chunin Exams. For example, she might have a more refined version of the Shadow Clone Jutsu, which surprises the opponents and judges. Her character could also show more emotional intelligence during the exams, like using her understanding of others' feelings to her advantage in battle, perhaps by predicting their moves based on their emotions.
One idea could be Naruto Namikaze facing off against a new and mysterious opponent during the Chunin Exams. This opponent could have a unique jutsu that Naruto has to figure out how to counter.
A fanfiction might explore the idea of Naruto and Kurenai teaming up during the Chunin Exams. Kurenai, being an experienced kunoichi, could guide Naruto through the more complex parts of the exam. They could face off against some unexpected opponents together. Naruto's raw power combined with Kurenai's intelligence and genjutsu skills would make for an exciting story.
One interesting aspect in Naruto fanfiction about Fuinjutsu in the Chunin Exams could be a character using unique Fuinjutsu techniques that were not shown in the original series during the exams. For example, a genin might create a sealing jutsu to temporarily disable an opponent's chakra flow in a creative way that surprises everyone.
In a Chunin Exams fanfiction, Naruto and Temari could be paired in a team - up for a special mission within the exams. Their personalities would clash at first. Naruto is all about enthusiasm and impulsiveness, while Temari is more level - headed. However, they gradually learn to work together. Maybe they face a powerful enemy that requires both Naruto's brute strength and Temari's strategic thinking to defeat.