Well, perhaps the OC reborn as Kurama tries to find a way to coexist peacefully with the jinchuriki in a different way than in the original story. They could use their unique perspective to broker better relationships between the tailed beasts and the humans. Maybe they also try to uncover secrets about the origin of the tailed beasts that were previously unknown.
A possible plot for 'oc reborn as kurama fanfiction' is that the reborn Kurama (the OC) has a special ability from their past life that changes the balance of power in the Naruto universe. This could lead to new alliances and rivalries. They might also try to change the fate of some of the side characters in the story, like helping a minor character become a powerful ninja by sharing their knowledge.
A really interesting plot could be that the OC is from a different dimension and accidentally ends up in Youko Kurama's world. They start off as strangers but gradually form a bond as the OC tries to find a way back home, and Youko Kurama helps them while also learning about this new and strange being. This can involve a lot of world - building and exploration of different cultures or powers.
One idea could be an OC who has a special power related to time manipulation in the 'hitman reborn' universe. They could use this power to change the outcome of battles or prevent certain tragedies. Another could be an OC that is a long - lost relative of one of the main characters and has a different view on the mafia world, causing some internal conflicts.
One idea could be that the OC, reborn as Naruto, uses their prior knowledge to quickly master jutsu. For example, they might know about the Rasengan from the start and be able to perfect it faster. Another plot could involve the OC changing the relationships in the village. Maybe they befriend Sasuke earlier and prevent his defection. Or they could introduce new ninja techniques from their past life to the Hidden Leaf.
Another plot could involve an OC reborn into the body of a criminal in the Naruto world. They have to struggle to redeem themselves and prove that they are not the same person as the original criminal. Along the way, they could discover the real reasons behind the original criminal's actions and try to right the wrongs that were committed.
One idea could be that the reborn OC genius uses their extraordinary intelligence to solve a mystery that has baffled the entire community. For example, they might figure out the secrets behind an ancient artifact's power.
One idea could be that the OC, now as Kakashi, has to deal with the same traumas Kakashi had but with a different perspective from their original self. For example, they might handle the loss of their comrades in a new way that changes the course of events in the Naruto world.
One idea could be to give the OC a new power or ability in their reborn state. For example, if it's a fantasy setting, they could gain the power to control an element they were previously weak against. Another idea is to change their personality slightly due to their rebirth experience, like becoming more confident or cautious. You could also explore a different backstory for the OC in the fanfiction, perhaps one that was hidden before their rebirth.
One idea could be an OC who has a unique power to communicate with Titans on a deeper level. This power could be a double - edged sword, as it might draw unwanted attention from both humans and Titans. Another plot could revolve around an OC who is a master of stealth and uses it to uncover secrets within the Walls. For example, they could discover hidden chambers or forgotten knowledge about the Titans.
A plot could involve Naruto having to go on a journey within his own mind to save Kurama from some sort of dark influence. During this journey, they discover hidden aspects of each other's personalities. Naruto might find out that Kurama has a soft side that he's never shown before, and Kurama could learn about Naruto's insecurities. This could lead to a stronger bond between them, and when they return to the real world, their combined strength is even greater. And as their relationship deepens, they face challenges from the outside world that test their new - found connection.
One idea could be that Naruto and Kurama have a day - out in the Hidden Leaf Village. They visit all the places Naruto used to go as a kid, like Ichiraku Ramen, and Kurama makes funny comments about human food. Another could be that they team up to prank the other villagers in a harmless way, just for fun.