A possible storyline is that Naruto and Sai get lost in a mysterious forest. In this forest, they have to rely on each other's skills. Naruto uses his combat and survival skills, while Sai uses his intelligence and artistic abilities to find a way out. Through this experience, their bond strengthens and they become even better friends.
Perhaps a fanfiction where Naruto and Sasuke are in a bit of a feud again, and Sai has to play the mediator. Sai, with his detached yet observant nature, tries to make Naruto and Sasuke see each other's points of view. This could lead to a series of events where they all grow as characters, learning about friendship, forgiveness, and the power of unity.
There might be a fanfiction where Sai tries to understand Naruto's deep bond with his friends better. Sai, being more reserved, could learn a lot from Naruto's open - heartedness and the story could explore their growing friendship in that context. It could involve them training together and Sai slowly opening up.
One interesting storyline could be Naruto finding himself in Artemis' realm. He might initially be confused by the different world but then start to learn about Artemis' powers and the nature of her domain. His ninja skills could be put to the test in a new and magical setting.
A cool storyline could be that Kurama gets a chance to experience the human world through Naruto in a more direct way. He gets to understand human emotions and relationships better, and this changes the dynamic between him and Naruto in unexpected ways.
One interesting storyline could be Naruto and Kurama forming a deeper bond beyond the usual jinchuriki - tailed beast relationship. For example, they might have to work together to save the Hidden Leaf from a new, powerful enemy that neither could face alone. This would involve Kurama sharing some of his ancient knowledge with Naruto to help in the battle.
One interesting storyline could be Naruto and Misty teaming up on a quest in a strange new land. Maybe they are searching for a powerful artifact that can save both their worlds. They'd have to combine Naruto's ninja skills with Misty's Pokémon handling abilities.
One interesting storyline could be Naruto joining Team 8 for a special mission. Maybe they are tasked with protecting a rare and powerful ninja tool. Naruto's unorthodox methods might clash with the more traditional approach of Team 8 at first, but they gradually learn to work together and combine their skills. For example, Naruto's shadow clones could be used in creative ways to scout out the area while Team 8 members use their tracking and stealth abilities to set up an ambush.
One interesting storyline could be a time - travel one where Naruto goes back in time and meets a young Mikoto. He could end up befriending her and changing some events in the Uchiha clan's history for the better. Another could be a story where Mikoto survives and she takes Naruto under her wing, teaching him some unique Uchiha jutsu.
One interesting storyline could be Naruto learning unique jutsu from each of the Sannin. For example, learning snake-based jutsu from Orochimaru in a way that doesn't corrupt him. Another could be a story where Naruto helps Tsunade overcome her fear of blood again in a new and dangerous situation. Or perhaps a tale where Jiraiya takes Naruto on a special mission that reveals secrets about the Sannin's past.
One interesting storyline could be Naruto and Kurama teaming up to face a new, powerful enemy that neither of them can defeat alone. They have to combine their powers in a unique way, like Naruto using Kurama's chakra in a more refined and strategic manner than ever before.