He might fit in by becoming a teacher or some sort of mentor at the school. Since he has such great power, he could teach the students new ways of using their own powers or just general combat skills. In the process, he'd get involved in all the drama and power struggles within the school, adding a new dynamic to the story. He could also have his own goals and motives that are slowly revealed as the fanfiction progresses.
Well, Naruto's friendly and outgoing nature would make him quickly form friendships in High School DxD. He could also use his ninja skills to outwit the devils and other supernatural beings in various challenges and competitions within the school. His ability to never give up would inspire the characters in this new world.
Naruto could also be a catalyst for change in the High School DxD world. His values of friendship and never giving up could inspire the characters there. He might introduce new ways of training or fighting. His ability to endure pain and keep going would be something that the characters in High School DxD, who are often more focused on power and status, could learn from. He could also bring a different perspective on the relationships between different species in that world, given his own experiences with different ninja clans and villages.
He could fit in as a mysterious new student. His transcendent powers would set him apart from the rest. He might initially be seen as a threat by some of the factions in the school.
Naruto could fit in as a powerful outsider. His physical abilities and combat skills would be highly regarded. For example, his speed and strength from his ninja training could rival some of the stronger devils in High School DxD. He would also bring his own sense of justice, which might be different from the devils' motives. This could lead to some interesting conflicts and resolutions.
One interesting plot could be Godlike Sans using his unique abilities to help the characters in High School DxD in battles. For example, his teleportation skills might give them an edge in combat against powerful foes.
Naruto could fit in as a new transfer student in the High School DxD universe. His out - of - this - world ninja skills would make him stand out immediately. He might initially be confused by the supernatural elements but would quickly adapt and use his skills to protect the school or his new friends from any threats.
Naruto could fit in as a new transfer student in the school from the Naruto world. He'd bring his unique ninja skills and his never - give - up attitude. His Rasengan could be a powerful new move in the battles against the various supernatural foes in the DxD world.
Goku's powers in a High School DxD fanfiction would be a game - changer. His ki attacks could be on a level that could potentially destroy entire areas in the DxD universe. His martial arts skills are also top - notch. In a fight, he would use his speed and agility to dodge attacks and then counter with his powerful punches and kicks. His transformation abilities, like Super Saiyan, would be a shock to the characters in DxD. They might not have any means to counter such a huge boost in power.
Goku Black could potentially enter the High School DxD world through a dimensional rift or some sort of magical accident. Once there, his Saiyan pride and his dark motives (from his own story) could lead to him either trying to take over the various factions in the DxD world or simply looking for a worthy opponent. He might interact with the main characters like Issei, perhaps seeing him as a target to prove his superiority or a potential ally in his own schemes.
Goku would fit in as a super - powerful outsider. His physical strength and combat skills are far beyond what the normal characters in Highschool DxD are used to. He could become a sort of protector for the school, using his powers to fend off any threats that come their way. His energy - sensing ability would give him an edge in detecting hidden enemies.