Naruto could be one of his allies. Naruto has this knack for seeing the good in people and would probably be willing to give Obito a chance to redeem himself. Also, Sakura, with her skills as a medic - ninja, could be an ally. She might help heal Obito if he was injured during the war and see the potential in him to be a force for good.
Hashirama's revival might also bring back old wisdom and knowledge. He could teach the new generation of shinobi things that have been lost over time. However, there could also be political issues. Some might not be happy with a long - dead Hokage coming back and potentially interfering in current affairs. And his revival could also have an impact on Naruto's own growth. With Hashirama around, Naruto might have to re - evaluate his role as a leader and a shinobi.
In some fanfictions, Naruto might use a powerful jutsu. Maybe he discovers an ancient sealing technique that can bring back the dead for a short time. He could also have found some rare chakra-infused artifact that has the power to revive the First Hokage.
One possible fanfic could be about Tsunade and Hashirama meeting in a time - travel scenario. Maybe Tsunade, who is known for her strong - willed nature, could go back in time and meet Hashirama, the first Hokage. They might initially clash due to their different leadership styles. Hashirama was more about unity and building the village, while Tsunade has a more no - nonsense approach. But as they get to know each other, they could learn from one another and form an unlikely friendship that would change the course of the ninja world in some small but significant ways.
There could also be interactions with the new generation of ninjas. They might view Obito as a sort of legend or a cautionary tale. Their fresh perspectives could either inspire Obito to change further or make him feel even more out of place in this new post - war ninja world.
Well, the reborn character could explore Obito's Sharingan powers in new ways. Instead of using them mainly for combat like Obito did in the original story, they could focus on using the Sharingan to understand the emotions of others. For example, they could use it to detect lies and hidden motives, which would be a unique twist on the power.
Besides Obito, Sasuke could be a main character in this fanfiction. Sasuke, with his own journey of redemption and his understanding of power and the ninja world, could have an interesting dynamic with the reincarnated Obito. Also, Sakura might play a role. She could be the one who tries to heal the reincarnated Obito, both physically if he is injured during his new adventures and emotionally from the traumas of his past life.
Often, Obito is attracted to Kushina's strength and kindness. He might try to impress her with his own abilities. Their interactions could involve Obito being a bit clumsy in his attempts at first. Kushina, on the other hand, might find his eagerness endearing and start to open up to him more. They could share stories about their pasts, their dreams, which deepens their bond.
The cells can also introduce internal conflicts. A character might struggle with the foreign power within them. They could be afraid of losing control, like Orochimaru was with his various experiments. This internal struggle is a great way to develop the character's emotional side and show their insecurities.