It could be an ancient shinobi who once tried to control the Kyuubi but was sealed away. Now, with Naruto as the new host, he sees an opportunity to take over the Kyuubi's power again.
One idea could be Naruto exploring the ancient powers of the Kyuubi that were long forgotten. He could discover hidden techniques that only the Kyuubi knew in its long existence.
One way to combine them creatively is through a crossover story. For example, Naruto could be transported to the Fairy Tail world and his Kyuubi powers could be mistaken for some kind of powerful magic. The characters from Fairy Tail might initially be cautious or even hostile towards Naruto because of his unknown and powerful abilities. But as the story progresses, they could learn to work together and Naruto could teach them about his world and his ninja skills while also learning about magic from the Fairy Tail mages.
Well, you could start by having a character from Fairy Tail accidentally stumble into the world where Kurama and Kyuubi exist. Then, they discover a connection to the Nuarto world through some ancient magic or prophecy. And from there, the story can unfold as they try to find their way back home while also dealing with the powers and politics of these different worlds.
Yes, in some fanfictions, Naruto is often depicted as the Kyuubi or having a very close connection to it. This can lead to really interesting and unique storylines that deviate from the original plot.
One common plotline is the Kyuubi teaching Naruto new and powerful jutsu. Since the Kyuubi has a vast amount of chakra and knowledge, it could share unique techniques with Naruto that are not part of the regular ninja training. Another plotline could be the Kyuubi's influence on Naruto's relationships. For example, some fanfictions explore how Naruto's connection with the Kyuubi affects how his friends and villagers perceive him. It can also lead to some interesting character development as Naruto has to learn to control the Kyuubi's power without being consumed by it.
In many Naruto fanfictions, Naruto might have developed some new and unique abilities that the Kyuubi has no defense against. This could make the Kyuubi, which is used to being a dominant and feared force, feel vulnerable. For example, if Naruto has the power to nullify the Kyuubi's chakra or to manipulate it in a way that goes against the Kyuubi's will, it would be a cause for fear.
Maybe it's because Naruto has some sort of special connection or resemblance to the Kyuubi that Kushina notices. For example, Naruto might display some of the Kyuubi's power characteristics in an obvious way that makes Kushina jump to that conclusion.
At first, Naruto might see the Kyuubi as just a source of power. But as he starts to protect it, he realizes it's more of a partner. Their relationship evolves from a simple user - power source dynamic to a deep - seated friendship. He begins to understand the Kyuubi's emotions and past, which further cements their bond.
Sasuke is often a popular character in these fanfictions. His relationship with Naruto can be further explored in the context of the Kyuubi's fatherly influence. Maybe Sasuke is initially skeptical of this new - found bond between Naruto and the Kyuubi but later comes to accept it. Sakura is also a common character. She might notice the changes in Naruto due to the Kyuubi's fatherly presence and be either supportive or a bit jealous. Kakashi could also be there. He might be observing Naruto's growth under the Kyuubi's guidance and offer his own wisdom as Naruto's former teacher.