One possibility is that Naruto's powers are misconstrued in the High School DxD universe. His ability to use chakra and his ninja skills might be seen as something abnormal and scary. So, his new 'friends' in the DxD world could betray him out of fear or jealousy. They might think he's going to disrupt the balance between the different factions in their world, like the devils, angels, and fallen angels.
In this fanfiction scenario, Naruto might have trusted someone like Issei from High School DxD. However, due to some misunderstanding or external influence, Issei could turn against Naruto. This could lead to Naruto having to fight against not only the forces that are native to the DxD world but also someone he considered a friend. It would be a really tough situation for Naruto, having to adapt to a new world and then face betrayal on top of that.
Well, Naruto would probably be the most energetic student there. His boisterous nature might either annoy or endear him to the other students. He'd likely be eager to take on any challenges, whether it's a fight with a devil or an academic test. His shadow clones could be used for all sorts of things, like attending multiple classes at once or helping out in sports events.
Naruto might teach some of his ninja skills to the students in the High School DxD. For example, his tree - climbing and water - walking techniques could be really interesting for them to learn. Rias could be intrigued by Naruto's determination and his never - give - up attitude. She might see him as a valuable addition to her peerage. And in return, Naruto could be fascinated by Rias's devil powers and the way she manages her group. They could also have some cultural clashes, like Naruto's more simple and straightforward ninja culture compared to the complex and often flamboyant devil culture in High School DxD.
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.
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.
Well, in 'naruto goes to high school fanfiction', Naruto could be the star athlete. His ninja skills would give him an edge in sports like track or martial arts. He might also get into trouble for using his unorthodox ninja moves during gym class. And there's a good chance he'll try to start a ninja club at school to share his passion.
Firebrand could be a student in the High School DxD setting who has a strange connection to the Naruto world. Maybe they have dreams or visions of the Naruto world and start to develop ninja - like abilities in the High School DxD world. This could lead to them being an outcast at first, but as they grow in power, they become a key figure in protecting the school from threats that are both from the High School DxD universe and potentially threats that have some connection to the Naruto world.
Well, it could be that Naruto, as a Nephilim, enters the High School DxD world. He might use his ninja skills along with his new Nephilim powers. Maybe he has to deal with the devils and angels in the school setting, while also trying to keep his identity a secret. He could form new alliances and rivalries within the school, all while facing challenges that are unique to this crossover world.
Perhaps in this fanfiction, Naruto and Kushina are reincarnated in the High School DxD world. They have to adapt to the new school life there. Naruto would surely stand out with his determination and fighting abilities. Kushina would be a motherly figure to some of the students who lack that kind of support. They both could change the balance of power between the different factions in the world.
In a Naruto - High School DxD fanfiction, the power levels would be really interesting to explore. Naruto's sage mode and tailed - beast forms are extremely powerful. In the DxD world, there are different power systems like the Sacred Gears. It would be fascinating to see how Naruto's powers interact with the powers of the DxD characters. For example, could his Rasengan be enhanced by a Sacred Gear? Or how would he fare against a devil's magic?
One possible scenario could be that Naruto characters are somehow transported to the world of High School DxD. Naruto's ninjutsu skills would be quite a shock to the devils and angels in that world. For example, Sasuke's Sharingan could give him an edge in battles against the supernatural beings in High School DxD. And Naruto's never - give - up attitude might inspire some of the characters there to face their challenges more bravely.