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.
One possible motive could be to use Sakura as a bargaining chip. If he has some sort of plan against Naruto or the Hidden Leaf Village, Sakura, being a close comrade of Naruto, could be very useful. He might think that by restraining her, he can force Naruto to come to a certain location or make concessions.
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.
One great Kakashi x Obito fanfiction is 'The Bonds We Share'. It delves deep into their relationship, exploring how their past experiences shape their interactions in a post - war Konoha. It shows their growth and how they come to understand each other on a deeper level.
One possible reason could be that Obito sees Naruto as a means to fulfill his own twisted ideals. Maybe he wants to shape Naruto into a weapon against the Hidden Leaf. Another reason might be that he feels some sort of connection to Naruto because of their shared experiences of being alone and ostracized in the past. He could also think that by taking Naruto as a baby, he can prevent Naruto from becoming the hero the village wants him to be, thus disrupting the balance in the ninja world.
One of the key elements is the sequence of tragic events. First, there was the accident during the mission where Obito was severely injured. Then, Rin's death which was a huge blow. Another important element is his relationship with Kakashi. The misunderstanding between them regarding Rin's death was a major factor. Also, his own sense of being a failure due to his physical state contributed to his downward spiral. All these elements combined to create his very sad story.