Sakura could be a great protagonist. She's already a strong character in the Naruto universe, and if she were to somehow be involved with the Juubi eye in a crossover, it would be interesting to see how she'd handle the new power. Maybe she could use it to enhance her medical ninjutsu in ways never seen before.
I think Naruto himself could still be a good protagonist even in a crossover with the Juubi eye. He's always been about breaking boundaries and achieving the impossible. With the addition of the Juubi eye, he could face new challenges and enemies. He might have to struggle with the darker aspects of the Juubi eye's power, as it's a very powerful and potentially dangerous ability. But, as we know Naruto, he'd try to find a way to use it for good and protect his friends and the village.
A character from another anime or game could be a good protagonist in this fanfiction. For instance, if a character like Ichigo from 'Bleach' were to cross over into the Naruto world and gain the Juubi eye. He already has his own set of powers, and combining them with the Juubi eye would create a really unique power dynamic. He could bring his sense of justice from his own world and apply it to the situations in the Naruto world while dealing with the new power.
One possible interesting plot could be a crossover where a character from another universe gains the Juubi eye in the Naruto world. This new power could disrupt the balance of power, leading to alliances and rivalries being formed in new and unexpected ways.
In this kind of fanfiction, Naruto becoming the Juubi would completely change the Naruto universe. It would mean he has an insane amount of power. He could potentially reshape the world, bring peace in a way no one expected. His relationships with other characters like Sasuke would also be very different. Sasuke might be both in awe and a bit jealous of this new power Naruto has.
One possible scenario in this fanfiction could be that Naruto gains the Juubi Ten - Tails Eye and his power skyrockets. He might use this newfound power to protect the Hidden Leaf Village from even greater threats. Maybe he could even use it to bring about a new era of peace in the ninja world, as his already strong will and determination would be enhanced by the power of the eye.
The Juubi eye could potentially be a key factor in the time travel plot. It might possess powers that allow the user to manipulate time or access different timelines. For example, it could open portals to the past or future. This would create interesting scenarios where Naruto has to use the Juubi eye's power to correct past mistakes or prevent future disasters.
Naruto would likely be one of the main characters. Since it's a Naruto - centered fanfiction, he'd be the one using the Juubi eye for time travel, probably to save the world or his friends. Sasuke could also be involved. Maybe he initially opposes Naruto's use of the Juubi eye for time travel but later realizes its importance. And there could be villains like Kaguya who might try to stop Naruto from using the Juubi eye's time - travel powers for their own evil purposes.
In fanfiction, if Naruto had the Juubi Eye, he would likely become extremely powerful. His already formidable combat abilities would be enhanced to a new level. He might gain new jutsu or have an even greater control over chakra. This could potentially change the entire Naruto universe's power balance, making him nearly unbeatable against his foes.
The plot could involve the Juubi's chakra influencing some of the demons in the Inuyasha world. Naruto arrives and has to figure out how to stop this chaos. He might teach Inuyasha some of his ninja skills, and Inuyasha in turn could show Naruto how to deal with the demons. They could also find that the Juubi has some ancient connection to a powerful artifact in the Inuyasha world, and they have to stop an evil force from using this connection for their own gain.
Well, one possibility could be that Naruto, with the power of the Juubi, enters the DxD world. He might use his ninja skills and the Juubi's immense power to face off against the devils and other supernatural beings in the DxD universe. Maybe he forms alliances with some of the characters there, like Issei and his friends, and together they fight a common enemy that threatens both the ninja world and the DxD world.
One possible plot could be that the Juubi from Naruto somehow breaks through dimensions and ends up in the Bleach universe. This could cause chaos as the spiritual energy in the Bleach world reacts to the Juubi's massive chakra. Ichigo and Naruto might team up to stop the Juubi. Naruto could use his sage mode and Rasengan techniques, while Ichigo uses his Bankai. They would have to learn to combine their powers and fighting styles to defeat the Juubi and send it back to its own universe.
A common theme is the clash of different power systems. Naruto has his chakra and various jutsu, while Inuyasha has his demon powers. When the Juubi is added into the mix, it creates a complex power dynamic.