One character could be a ninja with the power to manipulate time on a very small scale, like slowing down an opponent's attack for a brief moment. There might also be a ninja from a far - off land who has strange and powerful jutsu that Naruto has never seen before. These characters would all bring different dynamics to the secret group and Naruto's experience within it.
Well, one possibility could be that Naruto, with his ninja skills and strong sense of justice, joins Slade for a common goal like fighting a greater evil that neither could face alone. Maybe they team up to take on a powerful, shadowy organization that threatens both their worlds.
Well, one possible plot could be that Naruto, disillusioned with the Hidden Leaf Village after some major betrayal. He might start to see the Akatsuki's goals in a different light. For example, if the village wrongly accuses him of a crime he didn't commit, like they did with Sasuke in some ways. He could then be approached by an Akatsuki member who offers him a place in the group where he feels he can be understood. And Naruto, in his search for a new purpose and a place to belong, decides to join.
In this fanfic, Naruto might face tougher and more secretive missions. He could be trained in new and deadly ninja techniques specific to ANBU. Also, his relationships with other characters might change. For example, he might become more distant from his old friends as ANBU work often requires secrecy.
In the 'naruto joins amegakure fanfic', Naruto would probably face some challenges at first. The people of Amegakure might be suspicious of him. But he would gradually win them over with his determination and kindness. He could also introduce new forms of chakra control to the local ninjas, which would enhance their combat abilities.
One possible plot could be that Naruto, feeling ostracized in Konoha due to his jinchuriki status, decides to join Orochimaru. Orochimaru, seeing Naruto's potential, trains him in some dark and forbidden jutsus. Naruto might start to change, becoming more cynical. He could use his newfound powers against those in Konoha who once shunned him, leading to a series of battles between him and his former friends like Sasuke and Sakura.
In a 'naruto joins obito fanfic', it could start with Naruto being transported to a parallel dimension where Obito has already started his own ninja village. Naruto, seeing the potential in Obito's ideas but also the flaws, decides to join him. He helps Obito to correct his path. For example, Naruto could teach the ninjas in Obito's village about the importance of hope and not giving in to hatred. They could then work together to build a village that is a model for the rest of the ninja world, based on both Obito's and Naruto's ideals.
One possible plot could be that Naruto, disillusioned with the Hidden Leaf Village for some reason, like being wrongly accused or feeling betrayed. He then decides to join the Akatsuki. He might bring in new jutsu and a different way of thinking to the organization. His goal could change from protecting the village to perhaps finding a new way to bring peace in a more radical way.
Well, if Naruto joins Hive in a fanfic, he might bring his ninja skills. He could use his shadow clone jutsu to help with various tasks in the Hive world. Maybe he'd befriend some of the Hive characters and teach them about chakra.
Besides Naruto, Yugito Nii could be a main character. She is a jinchuriki in Kumo, just like Naruto is in Konoha. They could bond over their shared experiences of being hosts. And there could be some of the Kumo elders who play important roles. They might be the ones who oppose Naruto's entry at first, fearing he could bring trouble, but then as they see how he can contribute to the village, their opinions change.
There's also Killer Bee. Since he has a connection to the outside world and is a powerful ninja. Naruto and he could cross paths in Kiri. They might even have some rap battles or just share their ninja experiences. Another character could be Zabuza. Even though he's dead in the original story, in a fanfic, Naruto could somehow encounter his spirit or a young Zabuza - like character and learn some of his swordsmanship skills.