In naruto kuchiyose fanfiction, an interesting aspect could be the relationships between Naruto and his summoned creatures. For instance, he might form a deeper bond with one of his summons, like the toads. This could lead to the summon having a greater influence on Naruto's growth as a ninja. Additionally, some fanfictions might explore how Naruto's kuchiyose jutsu evolves over time, perhaps allowing him to summon larger and more powerful versions of his usual summons.
One idea could be a fanfic where Naruto discovers a new and powerful summon that no one has ever seen before. This summon could have unique abilities that help Naruto in a crucial battle against a powerful enemy.
Obviously Naruto himself is a very popular character in naruto kuchiyose fanfiction as the main user of the kuchiyose jutsu. Jiraiya is also popular since he taught Naruto about the jutsu. And the toads like Gamabunta are often featured as important characters as well, given their role in Naruto's summoning adventures.
One interesting idea could be the combination of Naruto's ninja skills with mecha technology. For example, Naruto might use his chakra to power up the mecha in unique ways. Another idea could be the new enemies that are created specifically for this mecha - Naruto concept, like robotic shinobi that require different combat strategies compared to normal foes. Also, the design of the mecha Naruto itself can be really cool, perhaps with features inspired by the Nine - Tails.
One idea could be to create a story where Naruto discovers a new and powerful fighting style from an ancient scroll. Another could be a fanfiction about a tournament among all the ninja in the Naruto universe, with unique rules and unexpected alliances. Or perhaps a story where Naruto has to fight an enemy who can copy his every move and he has to find a way to outwit them.
One idea could be a crossover where Naruto visits Equestria and meets Fluttershy. He could learn about her kindness towards animals and they could team up to protect the magical creatures there from some sort of threat. Another could be a story where Fluttershy somehow gets transported to the Naruto world and has to adapt to the more dangerous environment, while Naruto helps her understand the ways of his world.
One interesting idea could be the unique interactions between Naruto's ninja world and the monstergirls. For example, how Naruto's skills like the Rasengan might be used in situations involving monstergirls. Maybe he uses it to protect a monstergirl from other threats in the fanfiction world. Another idea could be the cultural clashes. Since Naruto has his own shinobi culture, and the monstergirls would likely have their own distinct cultures, seeing how they interact and adapt to each other can be really engaging.
A really cool fanfiction idea could be that Naruto and Elsa are both summoned by a powerful sorcerer in a different dimension. They have to work together to find a way back home. Along the way, they discover that their powers are connected in some way, like Naruto's chakra can enhance Elsa's ice powers and Elsa's ice can be used to create new jutsu for Naruto.
One idea could be exploring the different types of chains in the Naruto universe. For example, chains that are made from chakra and have special abilities like restraining powerful foes or sealing jutsu. Another idea is to create a story where a new character has a unique chain - based fighting style that surprises everyone in the Hidden Leaf Village.
One idea could be a story where Naruto discovers a new way to combine the Rasengan with his Sage Mode. He could use the natural energy to enhance the Rasengan's power and create a more devastating attack. Maybe he teaches this new technique to his friends at the ninja academy to inspire the next generation.
One idea could be to combine Naruto's spirit of never giving up with the Braveheart theme of fighting for freedom. Maybe Naruto could find himself in a situation where the Hidden Villages are under the control of an oppressive force, and he has to lead a rebellion, much like William Wallace in Braveheart.