Perhaps Demon Naruto, in his altered state, initially clashes with Itachi. But as they come to understand each other's motives, they form an alliance. Itachi could help Naruto control his demon side while Naruto provides the brute force they need in battles against powerful enemies like the Akatsuki leaders who have their own sinister plans for the world.
Another idea is that a curse is spreading in the ninja villages, and only Demon Naruto's unorthodox powers and Itachi's Sharingan can figure out the source. Along the way, they face challenges from both their own villages that don't trust them and the mysterious force behind the curse. As they work together, they develop a deep bond that changes the course of the ninja world.
A plot could involve Itachi coming back to life and trying to make amends with Sasuke while also having to deal with Naruto's newfound power. Itachi sees the bond between Naruto and Sasuke and tries to help them strengthen it further for the sake of the Hidden Leaf Village. He could train them in some of his unique jutsu.
Some fanfictions might explore a scenario where Itachi and Naruto have to go on a secret mission together. During this mission, they encounter various challenges that force them to rely on each other. Itachi's calm and calculated nature combined with Naruto's impulsiveness could lead to both comical and tense situations as they strive to complete the mission.
One plot idea could be that Demon Naruto is on a quest to regain his humanity and Ino, with her mind - related abilities, tries to help him. She might be the only one who can reach the part of him that is still Naruto beneath the demon exterior. Another could be that they are forced to team up against a common enemy that is threatening the Hidden Leaf Village. The demon powers of Naruto give them an edge in battle, but they also attract unwanted attention.
A possible plot could be that there is a prophecy about Demon Naruto and Kushina. They have to work together to fulfill this prophecy which involves saving the ninja world from a great disaster. Along the way, they face many challenges. Kushina helps Naruto come to terms with his demon side, and Naruto uses his power to protect Kushina from the various threats they encounter. Their relationship evolves as they struggle to complete their task.
One idea could be that Itachi survives his battle with Sasuke and teams up with Naruto to face a new, powerful enemy from the Otsutsuki clan. They combine their unique skills, Naruto's Rasengan and Itachi's Sharingan abilities, to take on this threat.
A possible plot could involve Female Itachi being an outcast in her own clan because she has different ideals. Naruto, who always believes in people, befriends her. They then start a journey to prove that her ideas can bring peace to the ninja world, facing opposition from both their own and other clans.
One idea could be a story where baby Itachi meets a young Naruto in a sort of alternate universe. Maybe Naruto stumbles upon a hidden place where baby Itachi is being kept safe. They form an unlikely friendship, and Naruto's positive energy starts to influence Itachi in a way that makes him question some of the darker paths he might take in the future.
One idea could be exploring Itachi's time in ANBU and how Naruto might have influenced his decisions secretly. Maybe Naruto, with his unique way of seeing people, could have made Itachi question his path in the ANBU more deeply.
One idea could be that the Kyuubi's power somehow interacts with Itachi's Sharingan in a unique way. Maybe Itachi is able to use the Kyuubi's chakra to enhance his genjutsu even further. Another plot could involve Naruto, with the Kyuubi inside him, teaming up with Itachi to face a common enemy that neither could defeat alone. For example, a new powerful Otsutsuki clan member arrives, and their combined skills are needed to save the village.
Maybe a fanfiction where Konan discovers a secret about Itachi that could change the way Naruto views him. This could lead to a complex web of relationships and a journey of self - discovery for Naruto as he tries to figure out who to trust. The story could also explore Konan's past more deeply in relation to this new discovery.