Well, one possible plot could be Naruto growing up under Danzo's influence. He might be trained in more underhanded and secretive shinobi techniques. For example, he could be taught to prioritize the village's security above all else, even if it means using morally gray methods. This would put him at odds with some of his friends who follow more traditional ninja values.
It could also be due to Naruto's outcast status in the village initially. Danzo might think that banishing Naruto would be an easy decision as Naruto doesn't have many supporters at first. He might believe that by getting rid of Naruto, he can maintain the status quo in the village and prevent any disruptions that Naruto's presence might cause in the future.
There's a fanfic where Danzo tries to manipulate Naruto for his own political gain. However, Naruto, being the perceptive character he is, quickly catches on. This leads to a battle of wits between them. In the end, Naruto uses his own brand of talk - no - jutsu to make Danzo see the error of his ways and they end up working together to reform the village's political system.
In a fanfic where Danzo gives Naruto the Sharingan, it could lead to a very different Naruto. Naruto might gain new abilities and a new perspective on the Uchiha. He could potentially master the Sharingan quickly with his strong willpower, but he would also have to deal with the dark side of the Sharingan, like the curse of hatred that often comes with it.
His personality would likely be more reserved and calculating. Since Danzo was a very secretive and shrewd character, Naruto might inherit some of those traits. He may not be as open and trusting as in the original series.
One possible motive could be revenge. Maybe the oc or someone close to the oc has been wronged by Danzo in the past. So, to seek justice, the oc decides to take him down.
Well, in such a fanfic, Naruto might turn against his friends. He could be made to use his power for Danzo's often shady purposes. For example, he might be forced to target those Danzo sees as threats to Konoha in a more brutal way than he normally would. His relationships would be severely damaged as his friends would be confused and likely try to stop him, not realizing he's been brainwashed at first.
The plot could involve Naruto having a philosophical discussion with Danzo. Naruto, with his idealistic views of peace and friendship, might try to sway Danzo from his more ruthless ways. They could talk about power, sacrifice, and what it really means to be a shinobi. Naruto could also demand answers from Danzo about the secrets he's been hiding from the village.
One idea could be a fanfic where Danzo actually manages to become Hokage through some underhanded means. Then Naruto has to find a way to expose his true nature and restore the rightful leadership to the village. Maybe he teams up with some of the other shinobi who were also suspicious of Danzo's actions all along.
It depends on the specific fanfic. Some authors might come up with this plot twist to explore different character motivations and conflicts. In others, it might not be the case at all.