The student could be from a different village or clan and is sent undercover to learn from Madara. As the student gets closer to Madara, they start to understand his motives and the true nature of power in the ninja world. They might then have to decide whether to betray their own village or side with Madara, leading to a complex web of relationships and plot twists.
One possible plot is that the OC, as Madara's student, gets involved in the Uchiha clan's affairs. The OC could be in a position where they have to choose between loyalty to Madara and what they believe is right for the clan. This internal conflict could drive the story forward as the OC tries to navigate the complex politics and power plays within the Uchiha.
The plot could revolve around Madara being an outcast among the students. Despite his great power, his ideas and his way of thinking might be too radical for the others. He could be trying to form his own group within the academy, with like - minded students who believe in his vision of a stronger ninja world. This would create a lot of conflict with the established order in the academy.
It could be another powerful ninja who sees the student as a threat to their own power or plans. Maybe someone who doesn't want Madara to pass on his knowledge to an outsider or a young upstart.
One idea could be an OC who is a time - traveler and meets Uchiha Madara in his prime. The OC could have knowledge of future events and try to change the course of history, leading to many power struggles and moral dilemmas.
One idea could be that the reincarnated Madara retains some of his past memories but is in a completely different world. So he has to adapt to new cultures and powers while still having his old ambitions deep inside. Maybe he tries to find a way to bring back the old ninja ways in this new world.
One idea could be that the OC is a time - traveler from a future where Madara's actions had led to a desolate world. The OC tries to change Madara's path. Another could be the OC is a healer who stumbles upon a wounded Madara and nurses him back to health, leading to an unexpected bond. Or perhaps the OC has a unique power that Madara is intrigued by and he tries to use it for his own purposes at first but then develops real feelings for the OC.
One idea could be a love triangle where the OC is caught between Madara's grand ambitions and Izuna's more personal loyalty. The OC might be a healer who tries to keep the peace between the two brothers while falling in love with both in different ways. For example, Madara's strength and leadership might attract the OC on one level, while Izuna's kind heart and protectiveness draw her in another way.
The OC would likely start as a relatively inexperienced ninja. Under Madara's tutelage, they would become more confident and skilled. For example, they might learn how to better control their chakra.
One idea could be that the oc retains some memories of their past life. So they use their knowledge to change things in the pjs world. For example, they might know of a coming danger and work to prevent it.
Perhaps the fanfiction could center on the unborn child's potential power. Madara might worry about the child being used as a weapon or a tool by his enemies. There could also be a side plot about the reactions of the other ninja clans when they find out about Madara's pregnancy, and how it might change the power dynamics in the ninja world.