Well, Naruto would probably face a lot of tough opponents. Since Sasuke has his own goals and might be with some powerful people, Naruto would have to fight his way through. He might encounter new jutsus and strategies that he has to overcome.
The setting of the fanfiction could be really interesting. It could take place in new and unexplored areas of the Naruto universe. Maybe Naruto has to travel through dangerous lands or hidden villages to find Sasuke. Along the way, he could meet new allies or enemies that add more depth to the story.
The relationship between Naruto and Sasuke is complex. In this retrieval fanfiction, their past memories together could play a big role. Flashbacks of their time at the ninja academy, their first missions, and the bond they formed could be used to heighten the drama of Naruto's quest to bring Sasuke back.
It could be some of the village elders. They were the ones who decided to banish Naruto, so they could continue to oppose him even when he's in exile. They might see his growing power and influence as a threat to their traditional ways of running the village.
Some of Naruto's former friends who have been influenced by the negative propaganda against him could also be antagonists. They might be misled into believing that Naruto has changed for the worse. They could actively oppose Naruto, either by trying to capture him or by preventing him from doing certain things. Another possibility is that there could be a hidden group within the village that has a vendetta against Sasuke and, by extension, Naruto for bringing him back.
In some fanfictions, Naruto may become more mature. After going through the arduous process of retrieving Sasuke, he realizes the complexity of relationships and the importance of his comrades more deeply. He might also become more reserved in his emotions, as the experience has made him more aware of the consequences of his actions and words.
Naruto may turn more cautious. The Sasuke retrieval was a dangerous and complex situation. In fanfiction, it could make him think twice before jumping into action. He may analyze situations more carefully to avoid potential disasters. For instance, he won't be as quick to engage in a fight without considering all the possible outcomes. This is a big change from his usually head - first approach. He may also become more protective. Having almost lost Sasuke, he could be overprotective of his friends and the village, constantly on guard to prevent any harm from coming to them.
In this type of fanfiction, Naruto could be banished to a far - off land. Maybe he discovers a new form of chakra or ninja technique there. He could also form a new community with outcasts like himself. As for the village, Sasuke might feel guilty about Naruto's banishment and try to convince the village elders to reverse their decision. But the political situation in the village could be complex, with some factions seeing Naruto as a threat even after he retrieved Sasuke.
Well, perhaps in the fanfiction, after bringing Sasuke back, Naruto discovers that there are some secrets that the village has been hiding from him all along. When he tries to expose these secrets, the village sees it as a betrayal and turns against him. He might then be forced to team up with some unexpected allies outside of the village to clear his name and fight for what he believes is right. It could also be that Sasuke's return actually brings some kind of curse or danger with it, and Naruto is wrongly blamed for it.
Friendship is a very common theme. Naruto's strong bond with Sasuke is at the heart of the retrieval arc in the original story, and fanfictions often explore this further. They show how Naruto's love for his friend drives him to go to great lengths to bring Sasuke back.
In a fanfiction, they could be involved in a race. Naruto's speed, Sasuke's sharingan - enhanced perception, and Hinata's byakugan - aided navigation could all play a part. Maybe they start off competing against each other but then realize that there's an outside threat during the race. So they put aside their differences and work together to overcome the threat, forging a stronger bond in the process.
In this kind of fanfiction, one possibility is that they go on a journey to discover new jutsu together. They might leave the Hidden Leaf Village to find a place where they can train without the constraints of the village rules. Maybe they encounter new and powerful enemies that force them to rely on each other more than ever, strengthening their bond.