Well, in many fanfictions, Naruto might use his strong will and the power of his Uzumaki heritage. His natural chakra reserves are huge, which helps. He also has a deep understanding of friendship and the tailed beasts' pain from his own experiences. So, he can connect with them on an emotional level and gradually gain their trust, thus being able to control them.
In such fanfiction, Naruto may gain the ability to heal himself more quickly. Since the tailed beasts possess a great amount of life - force energy, Naruto could tap into that to accelerate his own healing process. His mental abilities could also be enhanced. He would be able to withstand greater mental pressure and use the tailed beasts' collective wisdom to make better decisions in battles. Moreover, he could potentially create a chakra shield that is extremely strong, using the combined chakra of all the tailed beasts to protect himself and his allies.
The relationships can be developed through shared battles. When Naruto and the fem tailed beasts fight side by side against common enemies, they can start to trust each other more. For instance, if they face a powerful rogue ninja together, they'll learn about each other's combat styles and strengths.
Naruto is obviously one of the most popular characters. Since he has a strong connection to the tailed beasts in the original series, in fanfiction, he often takes on even more heroic and complex roles related to them.
Another plotline might involve the tailed beasts teaming up in a way that was unexpected. Say, all the tailed beasts decide to break free from their jinchuriki hosts at the same time and form their own alliance. This would create a huge shift in the power balance in the Naruto universe and force the ninja villages to reevaluate their relationships with the tailed beasts.
I'm not sure specifically as there could be many different takes on it. It might be about a character who has a special connection or power related to the tailed beasts, like being able to control them in unique ways or having some sort of prophetic knowledge about them.
Often, the main character would be the Sage of Tailed Beasts. They would be the central figure driving the story forward. There could also be other important characters such as the jinchuriki of the tailed beasts. For example, if the story is about protecting the tailed beasts, the jinchuriki would play a crucial role. And of course, there could be antagonists, perhaps villains who want to capture the tailed beasts for their own evil purposes.
In Naruto ten - tailed fanfiction, often the storylines are quite imaginative. The ten - tails is such a powerful and mysterious entity in the Naruto universe. Fanfictions might focus on the origin of the ten - tails in a different light. Maybe there are hidden secrets about it that were not explored in the original series. And it's always interesting to see how the characters' relationships change due to the presence of the ten - tails.
In many Naruto fanfictions, the concept of Naruto becoming the Nine - Tailed Fox can be really interesting. It could potentially change the entire dynamic of the story. For example, his relationships with his friends and foes might be completely different. He might be seen as a more dangerous and unpredictable force, which would lead to different reactions from characters like Sasuke or Kakashi.