Another concept is that Naruto is possessed by a spirit similar to the Ghost Rider. His friends initially fear him, but he has to prove that he can use this new power for good. He might have to learn how to use the power without being consumed by the rage and darkness that often comes with it.
I'm not entirely sure as there could be many different interpretations in such a fanfiction. It might involve Naruto having some sort of connection with the concept of death, perhaps as a rider who traverses the realms related to death in the Naruto universe.
One main feature is the combination of two distinct universes. The Naruto universe with its ninjas, chakra, and village politics, and the Kamen Rider universe with its cool suits and transformation devices. Another feature is the new power - up scenarios. For example, Naruto might get a Kamen Rider - style transformation that gives him new abilities to fight stronger enemies.
Well, one way could be Naruto having the Ghost Rider's chain weapon. He could use it in his combat style, like when he's facing tough enemies. Maybe the chain could be enhanced with his chakra, giving it new abilities.
Maybe Naruto discovers a magical artifact during one of his adventures. This artifact has the power to connect him with a dragon. Once he touches it, a dragon from a hidden dimension is summoned and Naruto forms an instant connection with it, thus becoming a dragon rider.
First, you need to study both universes well. Know the powers, personalities, and backstories of the characters from Kamen Rider Gaim and Naruto. Then, come up with an interesting concept for the crossover. It could be something like a portal opening between the two worlds.
First, you need to understand the basics of both universes. Know the characters, their powers, and the settings. Then, think of an interesting premise like a Kamen Rider arriving in the Naruto world. Next, plan out your plot. Decide how the characters will interact and what challenges they'll face.
One idea could be a story where a character has a bloodline that combines the powers of Naruto's ninja world and Kamen Rider's technology. For example, they could have the Sharingan-like ability to analyze Kamen Rider powers and use them more effectively. This would create a unique dynamic in battles.
One idea could be a story where Naruto is somehow transported to the DxD universe and meets a character with the Rider or Caster class abilities. They could team up to face a common threat that endangers both the DxD world and Naruto's own world in some way.
I really like 'Kabuto in the Hidden Leaf'. In this fanfiction, Kamen Rider Kabuto's character is inserted into the Naruto universe. He has to deal with the politics and challenges of the ninja villages. The author does a great job of showing how Kabuto's powers and his way of thinking contrast with the traditional ninja ways. It's a fresh take on both franchises.