In fanfiction, Naruto joining Orochimaru could make him a more complex character. He'd be exposed to Orochimaru's unethical practices, which could make him question the ninja world's values. He might develop a darker side, but also a deeper understanding of the gray areas. Sasuke would experience a transformation too. His relationship with Orochimaru would be a strange mix of mentorship and power struggle. He could become more ruthless, but also more calculating. His interactions with Naruto in this new setting would be full of tension and moral dilemmas.
Their relationship could become stronger. Facing the danger that Orochimaru represents together would force them to rely on each other more. They might start to understand each other's motives and fears better.
It would likely become more complicated. Sasuke has his own history with Orochimaru. If Naruto goes to Orochimaru for power, Sasuke might see Naruto as a rival in a different way. He could be jealous that Naruto is getting power from Orochimaru, or he could be angry that Naruto is making the same 'bad' choice he once did.
Naruto could develop a new sense of determination. He might be determined to not let Orochimaru's experiments define him. Instead, he could use what has happened as a motivation to become stronger in his own way. He may also start to study more about the type of experiments Orochimaru was doing, not to replicate them, but to find ways to counter any future threats related to that kind of science.
In fanfiction, the relationship between Sasuke and Orochimaru is often complex. Orochimaru saw Sasuke as a vessel for his own resurrection or as a powerful tool. Sasuke, on the other hand, initially sought power from Orochimaru to avenge his clan. However, Sasuke was always cautious and didn't fully trust Orochimaru. This dynamic creates a lot of interesting plot points in fanfiction, such as Sasuke's internal struggle between his desire for power and his awareness of Orochimaru's true intentions.
Kabuto is also common. He was Orochimaru's right - hand man. In fanfiction, he could be used to either further Orochimaru's plans against Naruto or he could have a change of heart and help Naruto against Orochimaru. His medical skills and knowledge of Orochimaru's secrets make him an interesting addition to the story.
Her character could develop in a more morally ambiguous way at first. Since Orochimaru is a rather shady character, she might start to question her own values. For example, she could become more ruthless in combat as Orochimaru's teachings are often about survival of the fittest. However, as she realizes the error of her ways, she could transform into a more empathetic and wiser character, having learned from her mistakes and the dark side she has witnessed.
The story would also change in terms of Naruto's relationships. His friends like Sasuke and Sakura would be very concerned and might try to stop him. This could lead to a rift between them. Naruto might gain new powers faster, but at a cost. He could start to lose his connection to his normal self and the Nine - Tails inside him might react negatively to the experiment.
It changes the Naruto universe in several ways. Firstly, Fem Orochimaru's actions would be different from the male Orochimaru's. Her motives for taking Naruto might not be as purely power - hungry. This could lead to different alliances and enmities. For example, some characters who were against Orochimaru might be more lenient towards Fem Orochimaru if she shows a more benevolent side. Secondly, Naruto's growth and development would be altered. Instead of following the path with Jiraiya, he's with Fem Orochimaru. So his jutsu and combat style might incorporate more of her unorthodox and perhaps more feminine - influenced techniques. Also, the perception of Orochimaru's lair or hideouts would change. It could be less of a spooky, evil - filled place and more of a place of mystery and potential redemption.
Naruto would likely become more secretive. Since Orochimaru is a very private and often devious character, Naruto might pick up some of those traits. He would probably keep things from his friends more often.
Well, it could make Naruto a much darker character. Instead of his usual optimistic self, he might be filled with vengeance. This would change the dynamics of his relationships. His friends would have to deal with this new, brooding Naruto. Also, it might slow down his progress in becoming a stronger ninja as he has to first deal with the trauma of the torture.