The Akatsuki could also play the role of antagonists. They might view Naruto as a valuable asset due to his Nine - Tails chakra. And with Orochimaru involved with Naruto, they could see it as an opportunity to either take Naruto for themselves or get rid of both Orochimaru and Naruto to prevent any interference in their own goals.
Danzo could be a main antagonist. He might see Orochimaru's interest in Naruto as a threat to his own plans for Konoha. He could try to eliminate Naruto or use him as a pawn against Orochimaru, all while hiding his true intentions from the rest of the village.
Another possibility is a rogue ninja who was once a victim of Orochimaru's experiments. This ninja could see Naruto as a new test subject for Orochimaru and try to stop Orochimaru from getting too close to Naruto. However, his methods of stopping Orochimaru could be just as cruel and dangerous as Orochimaru's own actions, making him an antagonist in his own right.
Another potential antagonist could be an enemy that Orochimaru and Sakura face together during her training. This enemy might have a vendetta against Orochimaru and see Sakura as an extension of him. So while Orochimaru is training Sakura, this new enemy could be the one causing the most immediate problems and danger for them both.
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.
Hermione could be one of the main characters. She might be suspicious of Orochimaru's teachings and try to convince Harry that it's wrong. She would be constantly researching about Orochimaru and the type of magic he's teaching Harry to prove her point.
One possible reason could be Naruto's unique power. Naruto has the Nine - Tails within him, which is an extremely powerful and mysterious force. Orochimaru, being a character always interested in power and forbidden jutsu, might be obsessed with Naruto in fanfiction because he wants to study or even obtain that power for himself. Also, Naruto's strong - willed personality and his ability to change the people around him could be fascinating to Orochimaru who has always been somewhat of an outcast in the Naruto world.
Well, if Naruto saves Hinata from Orochimaru in a fanfic, it might start with Hinata being captured by Orochimaru's minions. Naruto would immediately go on a rescue mission. He'd probably fight through Orochimaru's various snake - based defenses. And when he finally reaches Hinata, he'd defeat Orochimaru with a powerful Rasengan, and then carry Hinata to safety.
Perhaps in this fanfiction, Naruto has some sort of special power or transformation that he unlocks just in time to face Orochimaru. It could be related to his Nine - Tails chakra in a new and unique way. He uses this power to break through Orochimaru's defenses and save Hiruzen. Naruto might also use his knowledge of Orochimaru's weaknesses that he has learned either from Jiraiya or from his own past encounters with Orochimaru's minions.
One possibility is that Naruto discovers Orochimaru's lair through some clever detective work. He then sneaks in, avoiding all the traps. When he sees Orochimaru about to perform some sort of experiment on Hinata, Naruto jumps in and starts fighting. He might transform into his Nine - Tails Chakra Mode to gain an edge in the battle and save Hinata.
In 'Naruto second Orochimaru fanfiction', Orochimaru is the central figure. Alongside him, Kabuto might be a prominent character as he was Orochimaru's right - hand man. Another character that could play a major role is Sakura. Since she is part of Team 7 with Naruto and Sasuke, and any threat or plot involving Orochimaru would likely draw her in. Also, there could be new characters created specifically for this fanfiction that interact closely with Orochimaru.
Well, Naruto could potentially be used as a bargaining chip by Orochimaru. Orochimaru might try to trade Naruto for something he wants from Konoha, like secret jutsu scrolls or some kind of political power within the village. And Naruto, being the determined hero he is, would likely be constantly looking for a way to escape and foil Orochimaru's plans.
In some fanfictions, Naruto might go to Orochimaru seeking power. He could be tempted by Orochimaru's knowledge of jutsu. Maybe he thinks that by learning from Orochimaru, he can become stronger faster and be better able to protect his friends and the village.