In this fanfic, perhaps Naruto is hit with a powerful jutsu that messes with his mind. This jutsu makes him see the world from Pein's perspective. He then starts acting like Pein, using his powers in a more aggressive way. But as he continues down this path, he realizes that Pein's methods are ultimately wrong and he has to fight his own internal struggle to break free from this new mindset.
Well, one possible plot could be that Naruto, after experiencing some major event or loss, starts to question his own beliefs. He then begins to study Pein's ideology more closely. As he delves deeper, he finds some aspects of Pein's views on peace through pain relatable. Maybe he tries to reform Pein's ideas from the inside, while his friends are initially shocked and try to bring him back to his old self.
A plot could involve Naruto being sent to a parallel universe where he is Pein. He has to live Pein's life and understand his motives. As he does so, he discovers the traumas and events that led Pein to become who he was. Naruto then tries to use this knowledge to change the course of events in that universe, and in doing so, he also learns more about himself and his own limits.
The plot could involve the child trying to understand Pain's actions. Maybe the child is born after Pain's death and has to face the consequences of his father's actions in the ninja world.
Perhaps in the fanfic, Pein gives Naruto the Rinnegan to create a balance of power. With the Rinnegan, Naruto might face new enemies who are after this powerful dojutsu. He would then have to use his newfound power, along with his existing skills like Sage Mode and Rasengan, to protect his friends and the village. The story could also explore how Naruto's view of the world changes with this new power.
One possible plot could be that Naruto, disillusioned with the traditional ninja ways after facing some great betrayal in the village. He stumbles upon the teachings of Jashinism. At first, he's hesitant, but as he delves deeper, he starts to see the power it could offer him. He begins to adapt their rituals and beliefs, which causes a huge rift between him and his former friends. His new path makes him a target for those who oppose Jashinism in the ninja world, leading to many battles and a complex web of relationships being torn apart and rebuilt in new and unexpected ways.
One possible plot could be that Naruto has faced so many betrayals. Maybe his friends turn on him due to some false accusations. This shatters his warm - hearted nature, and he becomes cold as a defense mechanism. He starts to isolate himself and no longer trusts easily.
One possible scenario in a fanfiction where Naruto becomes Pein could be that Naruto is exposed to some dark jutsu that alters his mind. This jutsu might be related to the Rinnegan's power. As a result, he starts to adopt Pein's ideology of bringing pain to the world in order to create peace. His friends would be shocked and try to bring him back to his normal self.
In the fanfiction, Naruto could also develop new strategies for fighting. Pein is a strategic mastermind, and under his training, Naruto might learn how to better analyze his opponents, anticipate their moves, and come up with more effective battle plans. This could give him an edge in future battles against powerful enemies.
In such a fanfic, it could be that Naruto discovers some dark secrets about the village leadership. These secrets are so dangerous that the leaders try to silence him. Naruto refuses to be silenced and decides to break away from the village, becoming a missing nin. He then travels the ninja world, gathering allies who also believe in exposing these secrets and fighting against the unjust system of the village.
Sasuke would be extremely suspicious. He has always seen Naruto as his rival and a symbol of the village's hope. If Naruto starts acting like Pein, Sasuke would think it's some kind of trick at first. He might even be ready to fight Naruto to figure out what's really going on.
Perhaps Naruto becomes a nukenin in order to protect a secret that could endanger the village if it were to be exposed. He leaves the village to keep this secret away from those who might misuse it. In his journey as a nukenin, he could develop new jutsu in isolation, away from the constraints of the village's training methods.
Well, one possible plot could be Naruto facing various challenges within the village that require the leadership of a Hokage. He might have to deal with political unrest, new threats from outside, and also find ways to improve the lives of the villagers. For example, he could start new training programs for the younger generation to make them stronger shinobi.