I think 'naruto ten tailed beast fanfiction' can be really interesting. It often explores the power and mystery of the ten - tailed beast in unique ways. Some fanfictions might focus on how the characters interact with this powerful being, like Naruto's potential new jutsus or his changed relationships due to the ten - tailed beast's influence.
One idea could be that Naruto discovers a new ancient power source that fuses with his existing chakra, gradually transforming him into an 11 - tailed beast. This new form could give him abilities beyond what we've seen in the original series, like the power to manipulate time on a small scale. Maybe he uses this new power to go back in time and prevent some of the tragedies that occurred in the Naruto world.
You could write a tailed beast fanfiction where the tailed beasts are reincarnated as humans. They start to remember their past lives as tailed beasts slowly. This would lead to a lot of internal conflict as they try to figure out who they are now. They might also have to deal with the fact that they still have some of their tailed beast powers, which could attract unwanted attention from various groups in the world of the story.
One common theme could be power struggle. Since tailed beasts are very powerful, Sakura would have to deal with the new - found power and how it affects her. Another theme might be acceptance. How does she accept being a tailed - beast - like being and how do others accept her in this new role.
He could be experimented on by rogue ninja scientists. These scientists might have been researching ways to create super - powerful beings and see Naruto as the perfect test subject. They use some forbidden jutsu or strange technology to try and force the creation of an 11 - tailed form within Naruto.
One idea could be an oc (original character) who has a special bond with the Ten - Tailed Beast. Maybe the oc is a descendant of an ancient clan that was once tasked with protecting the beast. The story could follow their journey as they try to keep the beast hidden from those who would misuse its power.
One interesting fanfiction could be where Naruto has an unexpected and more powerful tailed beast transformation during a major battle. Maybe he combines the power of all the tailed beasts in a new way, surprising his enemies and allies alike.
Well, Naruto himself might still be a main character as he has a strong connection to the tailed beasts in the original series. He could be the one trying to understand and deal with the 10 - tailed beast in new ways.
Perhaps the tailed beast inside Sakura has a mind of its own. It could communicate with her and offer her different perspectives on the ninja world. This could lead to Sakura making choices that are different from what her friends expect. For example, she might try to broker peace with an enemy village because the tailed beast has shown her the futility of war. The story could also involve her training with Kakashi or other experienced ninjas to better understand and use the tailed beast's power.
First, do some research on the tailed beasts. Know their powers, their backstories, and how they interact in the original source material. Then, come up with an interesting concept. It could be a new adventure for the tailed beasts or a different take on their relationships. For example, you could start with a tailed beast that is suddenly separated from its jinchuriki and has to find its way back.