A 'Naruto in High School DxD' fanfiction could involve Naruto being transferred to the DxD school. He would stand out immediately with his orange jumpsuit. His Rasengan could be a very powerful move against the devils and angels in that universe. And his sense of justice would likely lead him to get involved in all the power struggles and protect the weak, just like he did in his own world.
In a Naruto and High School DxD fanfiction, there could be a scenario where the protagonists of both stories meet in a neutral dimension. Issei from High School DxD might be intrigued by Naruto's ninja skills and determination. Naruto, in turn, could be curious about Issei's Sacred Gear. They could start training together, sharing their knowledge and skills, and ultimately have to face a common enemy that threatens both their worlds.
A 'Naruto is God' High School DxD fanfiction would be full of interesting crossovers. Naruto's sage mode could have a different interpretation in the High School DxD world. He might use it to sense the auras of different supernatural beings more clearly. His relationship with the female characters in High School DxD could also be an interesting aspect. Maybe some of them would be in awe of his god - like status, while others might challenge him. And his moral code, which is influenced by his experiences in the Naruto world, would likely clash or blend with the values of the High School DxD world. This could lead to many complex and engaging storylines as he tries to navigate this new universe while being a god - like figure.
In such a fanfiction, we might see Naruto using his senjutsu to gain an edge in the battles that often occur in the High School DxD universe. His sage mode could give him an advantage against the various powerful beings in that world. The fanfiction could also delve into the relationships between Naruto and the different characters in DxD. Would he become friends with Issei? How would Rias react to Naruto's presence? There are countless possibilities for an exciting and unique story.
Asta could be brought into the High School DxD fanfic as a result of a multiverse - related event. In this case, different universes are colliding or being connected in some way. His presence would disrupt the power balance as his anti - magic is something that no one in the High School DxD world has really encountered before. He could end up training with the devils to learn more about their magic while also teaching them about the concept of anti - magic.
One way could be through the power system. The EMS (Eternal Mangekyou Sharingan) from Naruto could be a unique power that a character in the High School DxD world acquires. Maybe a transfer student from a hidden ninja village arrives at the high school and has to keep their EMS a secret while dealing with the devils and angels in the school. This could lead to some interesting battles and interactions as the powers of the EMS, like the ability to use powerful jutsus, contrast with the magic and abilities of the High School DxD characters.
One possible fanfiction could be about Naruto characters attending the school in High School DxD. For example, Naruto's positive and determined attitude might clash with the more complex social and power dynamics in the DxD world. He could make new friends or even rivals among the devils, angels, and fallen angels.