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.
In fanfiction, Goku Black might adapt to the High School DxD setting by enrolling in the school under a false identity. He could use his martial arts skills to participate in the Rating Games, the combat tournaments in the DxD world. His unique fighting style and superhuman strength would give him an edge. However, his different values from the DxD characters, which are often based on different power hierarchies and moral codes, would lead to many interesting conflicts and interactions.
His ki - based attacks would be a new and powerful addition. In High School DxD, most of the powers are related to magic, sacred gears, and demonic or angelic powers. Goku Black's ki blasts would be a completely different form of energy that could catch everyone off - guard.
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.
Naruto has a very outgoing and friendly personality. In the High School DxD world, he would probably try to make friends with everyone, regardless of their race or faction. This could lead to some very interesting interactions. For example, he might try to convince the devils to use their powers for more positive things, like protecting the innocent, rather than just for their own gain. And his skills in stealth and combat would make him a valuable asset in the battles that often take place in the High School DxD world.
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 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.
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.
Well, Naruto has a big heart and is always ready to help others. In the context of a High School DxD harem with Kuroka, he could use his knowledge of ninjutsu to teach the others some new combat techniques. His ability to make friends easily would also play a role. Kuroka, being a cat - like character, might be intrigued by Naruto's different species and his unique chakra. Naruto could also adapt to the different social norms of the DxD world and become an important part of the harem.
The chakra system from Naruto could be incorporated as a new form of power in the High School DxD world. For instance, Naruto's ability to use shadow clones could be used in battles or to play pranks at the high school. His Rasengan could be a super - powerful attack against the devils and fallen angels in that universe.
Well, the Naruto characters could enter the High School DxD world during a dimension - hopping accident. Once there, they could use their unique abilities to their advantage. For instance, Sakura's medical ninjutsu could be very useful in treating the injured in the DxD world, which is often full of battles. The Naruto characters could also form clubs or teams in the DxD school. Naruto might start a ninja - themed club, teaching the DxD students about stealth and quick combat. This would not only help them fit in but also create some interesting storylines as they interact with the local characters.