The story could progress in many ways. For one, Sasuke might be filled with guilt for receiving Naruto's eyes. This guilt could drive him to become a better person and fight for the things Naruto believes in. He may also use the new vision to uncover secrets or powers that were previously hidden. On the other hand, Naruto, without his eyes, could develop other enhanced senses or abilities, and together they could form a new kind of partnership. They could also face challenges from those who oppose the idea of Naruto sacrificing so much for Sasuke.
One possible reason could be their deep bond. Naruto and Sasuke have a complex relationship. Naruto has always wanted to save Sasuke from the darkness. Giving his eyes might be the ultimate way to show his loyalty and belief in Sasuke's redemption. It could also be because Naruto sees Sasuke as a part of himself, and sacrificing his eyes is like sacrificing for a part of his own soul.
The plot implications could be huge. It could create a new dynamic between Naruto and the Uchiha clan. Naruto would have a part of Uchiha heritage, which might make some Uchiha more accepting of him. Also, it could lead to new alliances as other villages might see Naruto as an even greater threat or an even more valuable ally. And in terms of character development, Naruto would have to deal with the new power and the potential darkness that comes with the Sharingan.
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.
If Naruto gives up his dream, Sasuke might view him as a weakling. Sasuke has always been competitive with Naruto, and Naruto's giving up could make Sasuke lose respect for him. Their relationship could become strained as Sasuke may distance himself from Naruto, thinking he is no longer the worthy rival he once was.
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.
At first, Sasuke would be filled with rage. His Sharingan was something he had cultivated and was a symbol of his Uchiha heritage. Naruto stealing it would be like stealing his very soul. He would immediately try to hunt Naruto down. But as he chases Naruto, he might start to think about the reasons why Naruto did it. He could consider if there was some greater threat that Naruto was trying to combat, but still, he would not be able to forgive Naruto easily and would demand his eyes back.
In the fanfiction scenario where Madara gives Naruto his eyes, Naruto's abilities would transform. Firstly, the basic Sharingan abilities would improve his reaction time and perception. He could analyze his opponents' moves better. With the potential for the Mangekyo Sharingan, he could gain unique and powerful techniques. For example, if he got a fire - based Mangekyo ability, he could combine it with his own Rasengan or other wind - based jutsus to create new and more powerful attacks. This would not only make him stronger in battle but also give him new ways to protect his friends and the village.
One possible reason could be that his eyes hold a special power that he doesn't want others to discover easily. For example, it might be a new type of Sharingan or a unique ability related to his Uzumaki heritage that he needs to keep secret to protect himself or those around him.
If Naruto gives up on Sasuke in fanfiction, the storyline could take a very different turn. For one, the whole dynamic of their relationship, which has been a central part of the original Naruto story, would be completely disrupted. Naruto has always been determined to bring Sasuke back to the village. Without that drive from Naruto, Sasuke might become even more isolated and perhaps fall deeper into the darkness. This could also lead to different power alignments in the ninja world. Allies of Naruto might question his change of heart, and enemies could take advantage of the rift between the two former friends.