One idea could be that Naruto is captured by an unknown enemy. While in captivity, he loses his sight due to some sort of dark jutsu used on him. His friends then embark on a journey to rescue him. In the fanfiction, they might face various challenges and new enemies along the way.
Well, without reading the specific fanfiction, it could be about Kurenai, a character from Naruto, capturing Naruto for various reasons. Maybe it's part of a mission, or perhaps there's some misunderstanding that leads to this situation.
It could be other villages as well. Since Naruto has made friends and allies from different villages during his adventures. For example, the Sand Village might send some of their ninja to help, considering Naruto's relationship with Gaara.
Another way is that he forms an unexpected alliance within Iwa. There could be a dissident group in Iwa who oppose the capture of Naruto. They might help him escape in exchange for some future favor or because they believe in Naruto's cause. Naruto has a way of inspiring people, even those who are initially his enemies, so this is a plausible scenario.
Sasuke could be a likely candidate. Despite their differences, Sasuke and Naruto have a deep connection. He might hear about Naruto's capture and come to his rescue, driven by their past friendship and the rivalry that also binds them.
Naruto would probably be defiant. He's not the type to just sit there and be a victim. He'd likely be shouting at his captors, telling them they made a big mistake.
Well, Naruto might escape by using his wits. He could pretend to be compliant with Orochimaru's plans at first, gain Orochimaru's trust a little bit, and then when Orochimaru least expects it, he could make his move. He could also find an ally within Orochimaru's lair. Maybe there's a henchman who has a change of heart and helps Naruto escape. Or, Naruto could discover a weakness in Orochimaru's security system or jutsu that he can exploit to get away.
In a 'naruto gets captured' fanfiction, he might be tortured for information. His captors could be after the secrets of his Nine - Tails chakra. They may try to use him as a bargaining chip against Konoha.
Well, it could go in many directions. For one, the Akatsuki might hold Naruto captive to use him as a bargaining chip against Konoha. They could demand things like the village's secrets or other powerful ninja in exchange for Naruto's life. Or perhaps some members of the Akatsuki would have a change of heart and decide to protect Naruto instead of following their original plan.