One possible motive could be to gain control over Naruto's power. Since Naruto has the Nine - Tails within him, Danzo might want to use that power for his own political or military gains. He's always been power - hungry and sees Naruto as a tool to achieve his goals of making Konoha stronger in his own way, which might involve more underhanded and controlling methods.
It could also be a completely new character introduced into the fanfiction. A foreign ninja who was inspired by some of Danzo's ideas (not the bad ones) and comes to Konoha to take on the role of successor, bringing in new perspectives and ways of doing things.
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.
Well, in some versions, Naruto might use his influence among the villagers. After Pain's attack, the village is in a state of rebuilding and re - evaluating. Naruto, being a hero, has the ears of the people. He could start by presenting evidence of Danzo's underhanded deals, like his connection to Orochimaru perhaps. Maybe he found some secret documents during the chaos that Pain caused, which link Danzo to unethical experiments or power - grabbing within the village.
He'll likely lose his power and influence in the village. Once Naruto reveals his secrets, the villagers won't trust him anymore. His actions might be put on trial, and he could be exiled from the village.
In lemon fanfiction, Danzo's character can add an element of mystery and conflict. His shadowy nature in the original Naruto series makes him a ripe character for fanfic writers to explore further. Tsunade, on the other hand, brings her strength and leadership. Together, they can create a dynamic where the power balance and their different outlooks on the ninja world are put to the test. Their characters can be used to explore themes like loyalty, power, and the cost of achieving one's goals in a more fictional and sometimes steamy context if the lemon aspect is involved.
One possible scenario in a fanfiction could be that Danzo secretly admires a female ninja from a distance. Maybe she's a skilled healer in the village. He might be drawn to her kindness and the way she devotes herself to helping others, but his position and his secretive nature prevent him from expressing his feelings openly.
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.
If Naruto was Danzo's grandson, it would completely change the Naruto universe. Naruto's ideals of friendship and trust would be in direct conflict with Danzo's methods. Naruto might have been trained differently, perhaps more secretly and with a harsher edge. It could also lead to a different dynamic with the other characters. For example, Sasuke might view Naruto even more suspiciously as he had a connection to Danzo, who Sasuke hated. And the village might have treated Naruto differently too, either with more respect due to his relation to a powerful figure or with more fear because of Danzo's controversial reputation.