One possible crossover could be in the area of combat techniques. Naruto's Rasengan could be combined with Rias's demonic powers in some way. Another could be in terms of leadership. Naruto, as a leader in his ninja village, and Rias, as a high - ranking devil, could share their leadership experiences. There might also be a crossover in terms of friendship. Naruto's friends like Sasuke and Sakura could interact with Rias's peerage members.
Well, perhaps the plot could center around Naruto's cousin being sent to Rias' world on a mission of sorts. Maybe there's a disturbance in the balance of power in Rias' realm that has an impact on Naruto's world too. The cousin, with his knowledge of Naruto's adventures, uses some of those learned tactics in the new world. He and Rias could form an unlikely alliance and as they get to know each other better, they start to share their respective cultures and powers, leading to a stronger bond between them and their teams.
Naruto's cousin might be initially cautious around Rias. But as he sees her leadership skills and determination, he would start to respect her. He could offer his ninja skills to help her in battles, like using his stealth to gather information. And Rias would be curious about his different power set and would try to learn more about his world.
In this fanfiction, their family connection might be the key to resolving some major conflicts. The two different worlds they come from probably have their own enemies. With their combined powers and the bond of family, they could face these threats together. Naruto's strong sense of loyalty and friendship could influence Rias and vice versa. This relationship could also attract the attention of other powerful entities in both worlds, who might either try to use it to their advantage or try to break it apart.
One possible fanfiction idea could be that Rias' sick brother is a key factor in a power struggle within their supernatural world. Naruto, being an outsider with his own set of skills and values, could get involved. Maybe he forms an alliance with Rias to protect her brother from those who would use his illness to their advantage.
They would likely start with some mutual curiosity. Naruto would be intrigued by Rias's devilish appearance and powers, while Rias would be interested in Naruto's ninja abilities. They might exchange stories about their respective worlds, with Naruto talking about his village and his friends, and Rias sharing about the devil society. Interaction could also involve sparring sessions to test each other's strength.
Definitely. The concept of combining different fictional universes in fanfiction is quite common. In a 'Naruto is Rias' Familiar' fanfiction, we could expect to see Naruto's ninja skills and powers being incorporated into the world of High School DxD. Maybe Naruto would use his shadow clone jutsu in battles in the DxD universe or his rasengan against some of the devils. It could also explore how Naruto, with his strong sense of justice and loyalty, would interact with Rias and the other characters in her peerage.
In this fanfiction, Naruto might show his jealousy in his typical brash way. He could be all fired up and ready to challenge the person who is making him jealous. Rias, on the other hand, would be more calculating in her jealousy. She might use her devilish powers and influence to subtly drive a wedge between the person causing the jealousy and the object of her affection. They could end up teaming up to get rid of the 'competition' in a rather comical or intense way depending on the tone of the fanfiction.
It's quite possible. Fanfiction writers often come up with interesting and unexpected concepts. Since Naruto and the world of Rias have their own distinct fan bases, combining them in a story where Naruto is a fan of Rias can add a new and exciting twist. You could also check fan - run forums dedicated to either Naruto or High School DxD to see if anyone can point you in the direction of such a fanfiction.
One possible reason could be that the storylines in the fanfiction are focused on different aspects or relationships within the fanfic's universe. Maybe the author wants to explore other characters' interactions more deeply and Naruto just doesn't fit into those particular plotlines they have in mind.