In the manga, Sasuke doesn't regain his Rinnegan. The story progresses without this particular change. The power he had before is maintained without reverting or regaining additional abilities related to the Rinnegan.
Naruto's character would change in multiple aspects. First, he would have to adapt to the new abilities of the Rinnegan. This would require him to study and train more, making him more focused and perhaps a bit less impulsive. Second, the power of the Rinnegan might give him a different perspective on the ninja world. He might start to see the power struggles and politics in a new light. Third, his relationships with his friends, especially Sasuke, would be different. Since he now has a part of Sasuke (in the form of the Rinnegan), their bond could become even more complex and deep. And finally, he might face new challenges in terms of his identity, as he is now not just the Nine - Tails Jinchuriki Naruto, but also the wielder of the Rinnegan.
Sasuke's reaction could be complex. At first, he would be enraged. After all, the Rinnegan is a symbol of his power and his journey to gain strength. However, he might also have some mixed feelings. He and Naruto have a deep bond, and he might wonder if Naruto had a good reason for taking it. But overall, his initial reaction would likely be one of fury and a desire to get his power back.
Their relationship would likely become more complex. With the Rinnegan involved, they might have to rely on each other more for understanding its powers. They could become more protective of each other, knowing the power and the danger it brings.
Well, Naruto's fighting style would change in multiple ways. Firstly, he would gain access to the six paths techniques that the Rinnegan allows. This means he could use things like the Deva Path's gravity manipulation in combat. Secondly, his speed and reaction time would be enhanced due to the Rinnegan's perception abilities. And finally, he might start to use more genjutsu - like tactics, since the Rinnegan has certain genjutsu - related powers. All in all, his fighting would become a more well - rounded and dangerous style.
Well, it could lead to a major shift in the power balance among the characters. Sasuke would be weakened without his Rinnegan, and Naruto would have to deal with the new power. There might also be some internal conflict within Naruto as he tries to come to terms with using Sasuke's power. Maybe he would feel guilty at first, but then realize it's for the greater good. Also, other characters like Kakashi or Sakura might have different reactions. Kakashi could be worried about Naruto being corrupted by the power, while Sakura might be more concerned about Sasuke's well - being without his most powerful ability.
If it's a crossover with the Fairy Tail guild, Natsu would be an interesting character to pair with Sasuke. Natsu is hot - headed and Sasuke is brooding. Their personalities contrast but they are both extremely powerful. Sasuke's Rinnegan powers could be used in combination with Natsu's fire - based magic in battles against powerful enemies. And they could have some great banter as they try to understand each other's worlds.
One idea could be a story where Sasuke, with his Sharingan, discovers a new power related to the Rinnegan that was hidden within Naruto all along. Maybe Naruto has some dormant Sage of Six Paths energy that when combined with Sasuke's powers, they can unlock a new level of strength to fight a powerful, unknown enemy.
The plot might involve Naruto with the Rinnegan being a bit of an outcast in the village at first because of the strange and powerful new dojutsu. Fem Sasuke could be the one to understand him and encourage him to embrace it. They could then go on a quest to discover the origins of the Rinnegan together, facing various challenges along the way, like ancient ninja traps and powerful, long - forgotten clans.