Percy's character would be much more of a warrior. In Sparta, they were bred for war. Percy would have a different mindset. He'd be more aggressive in combat and less hesitant to use force. His sense of honor would be deeply ingrained in the Spartan way. He'd also be more used to a hierarchical society, so his interactions with others might be more formal. For example, he'd show more respect to his superiors based on their rank. His relationship with the gods would also be different. He'd have to hide his connection to Poseidon more carefully as the Spartans had their own pantheon of gods they revered, and any deviation from that could be seen as heresy.
His sense of honor might be different. Spartans had a strong code of honor. Naruto, as the grandson of Sparta, would likely have a more rigid view of honor. He might be less willing to make compromises that go against his newfound sense of honor, which could lead to some interesting conflicts with his friends and the Hidden Leaf Village, as they are used to his more flexible approach.
Well, Percy's relationships would have some interesting changes. For example, with the new campers at Camp Half - Blood, he might be seen as an oddity at first. Some might avoid him, while others would be curious. His relationship with Chiron would be different too. Chiron would have to find new ways to train him, focusing more on his other senses and his mental abilities. And when it comes to romantic relationships, it would be more challenging for Percy. He would have to rely on other things than just looks to attract someone. But this could also lead to more meaningful relationships, as the person who falls for him would be attracted to his inner strength, his courage, and his ability to adapt to his blindness.
Percy's development would be centered around survival and power. In Tartarus, it's all about being strong enough to endure. So he would be more focused on getting stronger. He might also be more isolated, as not many would understand his Tartarus - born nature. His relationships would be more difficult to form and maintain. He would have to learn to control his powers, which might be more closely related to the dark forces of Tartarus, without being consumed by them.
Her character would be different in several ways. Physically, she'd face different challenges. For example, if there are tasks that require a certain level of physical strength that were easier for male Percy, female Percy might have to find alternative ways to overcome them. Emotionally, she could be more empathetic. Since society often expects girls to be more nurturing, she might show more concern for the well - being of others. This could also change her leadership style. Instead of a more authoritative leadership, she might lead by example and through building consensus. And her sense of identity would be more complex. She'd have to balance being a girl with being a demigod, which could lead to some interesting internal conflicts.
Percy's relationships would be in upheaval if he were born a werewolf. His friendship with his demigod comrades at Camp Half - Blood would face many challenges. Some might be accepting, but others would fear his new - found abilities and the potential danger he poses. His relationship with his father, Poseidon, would also be altered. Poseidon might see Percy as more of an abomination or a unique tool depending on his own complex nature. Percy's love life, like with Annabeth, would be full of complications. Annabeth would have to decide if she can love a werewolf - demigod hybrid, and Percy would struggle with his own self - image in relation to her. His relationships with other mythological creatures, such as centaurs and nymphs, would also change as they would view him through the lens of his werewolf nature rather than just his demigod status.
He'd be more confident. Having that much power at his fingertips would make him less hesitant in dangerous situations. He might become a bit more arrogant too, as the Infinity Gauntlet could easily go to one's head.
Well, the plot could involve Percy being born in Sparta during a time of great unrest. The city - state might be facing a mysterious plague or some sort of curse. Percy, with his demigod abilities, starts to notice things that are off. He could discover that it's the work of a minor god who is jealous of Sparta's fame. Percy then has to go on a quest within the city - state to find a way to stop this god and save Sparta, all while trying to fit in with the Spartan way of life which is very different from what he's used to in modern times.
Percy's power set would be different. Instead of just relying on his demigod powers, he would have access to Uchiha abilities. This would make him more complex in combat. He could be more strategic, using the Sharingan to analyze his opponents' moves before striking. Also, his relationships with other characters might change. Some might be afraid of his new powers, while others might try to use him for their own gain.
He would likely be more in tune with the earth and the sky elements. His powers might not just be limited to water control as before. For instance, he could have the ability to manipulate the ground like Gaia's children and also have some control over the air or weather like related to Ouranos.
If Percy was born a Roman in fanfiction, his allies would change a great deal. He'd be part of the Roman demigod community, so he'd be friends with those who follow the Roman way. For instance, Frank Zhang could be a closer ally. Frank has his own unique powers and a strong sense of loyalty to the Roman camp. Percy would also have to deal with different internal politics within the Roman camp as an ally. Regarding enemies, the Titans and Giants might view him as a more significant threat. Since the Romans were seen as a powerful military force in the mythology world, they might target Percy more aggressively to try and disrupt the Roman order and power structure.