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.
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.
One plot implication could be a shift in the power balance in the Naruto universe. With Naruto having the Rinnegan, the Akatsuki or other villainous groups might see him as an even greater threat and target him more aggressively. Another aspect could be the relationship between Naruto and Sasuke. Sasuke giving away such a powerful ability shows a great deal of trust and sacrifice. It could lead to a deeper bond between them, and they might team up more often to face new challenges.
It could make Sasuke more protective of Naruto. Sasuke has always had a complex relationship with Naruto, and seeing him lose an arm would stir up some deep emotions. He might feel guilty, especially if he was somehow involved in the incident that cost Naruto his arm. This could lead to Sasuke staying closer to Naruto and being more open about his feelings.
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, 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.
Well, if Sasuke gives Naruto his Rinnegan in fanfiction, Naruto's abilities would be greatly enhanced. The Rinnegan is extremely powerful, granting abilities like the Six Paths techniques. Naruto might gain better control over space - time, be able to use powerful gravitational and repulsive forces more effectively, and perhaps even access new forms of chakra manipulation. This could make him an even more formidable opponent, able to take on stronger enemies with ease.
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.