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.
One great Naruto Kamen Rider Gaim fanfic is 'The Crossover Quest'. It combines the unique elements of both universes really well. The characters from Naruto interact with the Kamen Rider Gaim characters in a very engaging way, and the plot is full of action and mystery.
One interesting fanfiction could be where the characters from Kamen Rider Gaim end up in the Naruto world. Maybe they team up with the ninja to fight a common enemy. For example, they could use their unique Rider powers along with ninja techniques.
A good Naruto Kamen Rider Gaim fanfic should have a well - thought - out plot that blends the two universes seamlessly. For example, it could explain how the powers from Kamen Rider Gaim would function in the Naruto world.
In terms of character crossovers, Ruby could be fascinated by Gaim's transformation abilities. She might try to understand the mechanics behind it, thinking it could be a new form of power similar to her own Crescent Rose. And Gaim could learn about teamwork from RWBY's team dynamic.
First, know the characters well. Study their personalities, backstories, and relationships in the original series. This will help you write them in a way that is true to the source material. For example, Kamen Rider Gaim is often brave but also has a sense of humor, so include these traits in your story.
Another plot could involve Kamen Rider Gaim getting trapped in a time loop. He has to relive the same day over and over again, each time trying to figure out how to break the loop while also dealing with the day - to - day threats he usually faces. In the process, he discovers new things about his powers and the true nature of the threats in his world.
One challenge is combining the two very different universes. Naruto's world is full of ninjas, chakra, and a feudal - like society. Kamen Rider Decade's world has high - tech elements and the concept of Riders. Merging these two concepts without making it seem forced can be difficult. Another challenge is staying true to the characters. Naruto is known for his determination and his goal to become Hokage, while Decade has his own mission to travel through different Rider worlds. Keeping their personalities intact while putting them in new situations is not easy.
One interesting Kamen Rider Decade fanfiction could be about Decade traveling to different Rider worlds and teaming up with alternate versions of himself. For example, he might meet a younger version of himself in the Kuuga world and they have to work together to defeat a new, powerful enemy that is threatening all Rider worlds.
Natsumi Hikari is a popular character in Kamen Rider Decade fanfiction. She provides a sort of 'normal' perspective in the otherwise extraordinary world of Riders. Writers might explore her growth from being a somewhat reluctant companion to Decade to becoming a more confident and important part of his adventures. Her relationships with other characters, especially Decade, are often a focus in fanfiction.