A more in - depth fanfiction could be about Jinx being a long - lost relative of a ninja clan in the Naruto world. Maybe she has some latent ninja abilities that she doesn't know about. Naruto helps her discover these powers and she has to choose between her old life of mayhem and a new life as a ninja, with Naruto guiding her through the process.
Another concept could be a fusion of their powers. Imagine if Naruto was somehow able to absorb Frieza's power or vice versa. This could create a new and extremely powerful being. The story could explore how this new entity would interact with the two different universes. Would it be a force for good or would the power corrupt it? There could be a lot of internal conflict as the combined Naruto - Frieza entity struggles with its new identity and purpose.
Another possibility is that Godzilla somehow ends up in the Naruto world. The shinobi might initially see it as a great threat, but Naruto could try to communicate with it using his ability to sense emotions. Maybe Godzilla is there because it's being chased by an even greater enemy from its own world, and Naruto and his friends decide to help it.
One idea could be a crossover where Naruto characters are transported to the world of DMC 5. For example, Naruto himself could end up in Red Grave City and team up with Dante to fight demons. His ninja skills like shadow clones and rasengan could be interestingly combined with Dante's devil may cry style combat.
In a Naruto - For Honor fanfiction, the Akatsuki members could be a part of the story. They could form a sort of mercenary group within the For Honor world. Their unique abilities and personalities would make for interesting interactions with the native For Honor characters, like the Samurai and Vikings.
Maybe Hercules is somehow sent to the Naruto universe. He would be this super - strong figure among the ninjas. He could learn some ninja techniques, like how to use chakra, which is different from his own strength. And his great strength could also be an asset in the battles in the Naruto world, especially against the big - bad villains like Pain.
Maybe a story where Revy is sent to the Naruto universe. She could be seen as a strange and powerful outsider. Her combat skills with guns would be a unique addition to the battles in the Naruto world. And perhaps she would form an unlikely alliance with some of the ninja clans.
One idea could be to have Naruto enter the world of Bloodborne. Maybe he is on a mission and accidentally gets transported there. He would have to deal with the dark and dangerous creatures using his ninja skills. His chakra could be an interesting element in this world, perhaps being mistaken for some sort of otherworldly power by the inhabitants of Bloodborne.
Maybe a story where the Akatsuki members from Naruto are involved in the Kakegurui school's gambling underworld. They could be using their unique powers and abilities to gain an edge in the games. Sasuke might use his Sharingan to read his opponents' tells during a card game, adding a new level of intrigue to the Kakegurui concept.
Another concept is that Euphemia discovers a strange portal and steps through it, ending up in the Naruto universe. There, she befriends Naruto and his friends. She could use her diplomatic skills to try and bring peace between the warring ninja clans, while also learning some ninja techniques herself.
Another fanfiction concept could be that Hachishakusama is somehow summoned into the Naruto world during a battle. Naruto and his friends initially think it's an enemy but then realize it's a being from another dimension. They have to figure out a way to send it back, perhaps by using some ancient sealing jutsu that Naruto has to learn specifically for this task.