First, get to know the universes well. Understand the power systems in Naruto like chakra and the nature of the Kyuubi. Also, study the magic types and guilds in Fairy Tail. Then, think of an interesting premise for the crossover. It could be a quest that involves both Naruto and Fairy Tail characters. Keep the characters' personalities true to their original versions.
One interesting story could be about a Kyuubi character in the Fairy Tail world having unique magical abilities that help the guild in a major battle. For example, it might use its nine - tailed powers to create powerful shields or offensive spells against a dark guild.
There are quite a few interesting Naruto, Kyuubi and Fairy Tail fanfictions out there. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Some fanfictions might focus on crossovers, where characters from Naruto and Fairy Tail interact in unique ways, and the Kyuubi could play a crucial role in the story, perhaps as a source of power or a mystery to be solved.
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.
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.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fan - created stories, and you can use the search function to look specifically for Kyuubi and Fairy Tail fanfiction. Just type in the relevant keywords, and you should be able to find a variety of works.
There might be a fanfiction that focuses on how the powers of Kurama and Kyuubi could be incorporated into the Fairy Tail magic system. For example, a mage in Fairy Tail discovers a way to use their chakra like abilities. As for Nuarto, it could be a backdrop for a new kind of magical beast in the story. It really depends on the creativity of the writer.
He could play the role of a powerful outsider. Since he has the power of the Kyuubi, he would be seen as a very strong and potentially dangerous individual in the Fairy Tail world. He might be initially shunned or feared, but as he shows his good intentions, he could become a respected ally. For example, in battles against powerful dark mages, his Kyuubi - enhanced strength and speed could turn the tide.
Naruto would likely be curious about the magic in Fairy Tail. He might try to learn some spells. The Kyuubi, on the other hand, could be a source of fear for some of the Fairy Tail members at first. Natsu might see Naruto as a rival in terms of strength and want to have a friendly fight. Lucy would probably be intrigued by Naruto's story and the Kyuubi. She might offer to help him understand the Fairy Tail world better.
I'm not sure there are many fanfictions specifically about Kyuubi getting the 10th tail. It could be a very unique and creative concept. Maybe in such a fanfiction, Kyuubi's power would reach an unimaginable level. It could change the whole Naruto world, perhaps leading to new alliances or battles as other characters react to this new, extremely powerful Kyuubi.