I'm not sure specifically as there could be many different plots for such a fanfic. It might involve Naruto characters being transported to the X - Men world or vice versa, and then they have to deal with the different powers, cultures and challenges in that new world.
The plot could involve Naruto characters being transported to the X - Men world or vice versa. They might team up to face a common threat that is affecting both worlds, like a powerful villain who is stealing chakra and mutant powers. Maybe Naruto and Wolverine could bond over their shared experiences of having a power within them that they have to constantly control.
Definitely Naruto from the Naruto series. And from the X - Men, characters like Wolverine or Professor X are very likely to be main characters as they are some of the most well - known X - Men.
I think Naruto and Rogue would be an interesting pairing. Naruto has a strong will and positive energy, and Rogue is always worried about her power harming others. Naruto could perhaps help Rogue gain more confidence in herself and her abilities. Also, his chakra might interact in an unexpected way with Rogue's power - absorption ability.
It could be about Naruto existing in two different realms or having to navigate between two contrasting aspects of his world. Maybe it's about his life as a ninja and his inner self which are like two separate worlds.
Naruto is the main character without a doubt. Besides him, characters like Hinata could be important. Hinata has deep feelings for Naruto, and if Naruto is in a strange state of being between two worlds, Hinata might play a role in bringing him back or helping him through it. Also, Pain could be a significant character if the two worlds are related to the different ideologies that Pain and Naruto represent, such as Pain's view of a world in pain and Naruto's view of a world at peace.
Well, you could start by having a common villain. For example, the Green Goblin could team up with a mutant - hating group. This would force Spiderman and the X - Men to work together. Spiderman might be initially against the X - Men because he's not used to their way of doing things, but as they face the common threat, they start to understand each other.
One possible plot could be that Naruto is on a mission in his world and gets caught in a powerful jutsu that sends him to the X - Men's universe. There, he's in danger as he doesn't understand this new world. Rogue senses his distress and saves him from some immediate threats like angry mobs who are scared of his strange appearance. Then they start to communicate, with Naruto trying to explain his situation using hand signs and simple words, and Rogue trying to understand and help him get back home.
One way their worlds could collide is through a cross - dimensional rift. Maybe Naruto is on a mission and accidentally gets sucked into the X - Men's universe. Rogue, being the curious and empathetic character she is, might be the first to approach Naruto. She could be intrigued by his unique chakra powers. Naruto, on the other hand, would be completely bewildered by this new world full of mutants with strange abilities.
The values of the two worlds could also merge. In Naruto's world, the concept of protecting the village and comrades is very important. In One Piece, it's about the crew and the pursuit of dreams. Characters from both worlds could learn from each other. For instance, the Straw Hat crew could learn about the loyalty within a ninja village, and the ninjas could understand the freedom - loving spirit of the pirates. This would lead to new character developments and story arcs in the fanfic.
I'm not sure specifically as I haven't read this novel. It might be about a journey or exploration that occurs between different realms or worlds, perhaps involving characters who are caught between two different existences.