Some of Ben's more heroic aliens, like Upchuck, could have really funny interactions. Upchuck might accidentally eat some of the devil fruits or other magical items in the DxD world, causing all sorts of wacky effects. And the angels in DxD might be initially suspicious of Ben, thinking he's some kind of new unknown entity. But as they see him fight against common enemies, they could start to respect him. Ben, on the other hand, would find the whole concept of the different supernatural races in DxD fascinating and might want to learn more about their powers.
Ranma would probably be very confused at first when he enters the Highschool DxD world. He might be skeptical of the devils and angels. Issei, being a pervert, might be really interested in Ranma's female form. But Ranma would likely not tolerate Issei's behavior easily. Kuno from Ranma 1/2 might see the DxD characters as new rivals for Ranma's affections. And the female characters from DxD could be intrigued by Ranma's martial arts skills and his tough - yet sometimes clumsy - personality.
The Fairy Tail characters are used to a world full of magic and guilds. When they enter the Highschool DxD world, they would bring their sense of camaraderie and loyalty. Characters like Erza would immediately assess the situation and try to find a way to protect her friends. In the DxD world, she might find some kindred spirits in the more honorable devils. Meanwhile, the Highschool DxD characters are used to a world of different species and complex power dynamics. They would be curious about the Fairy Tail magic. For instance, the magic items used in Fairy Tail could be very appealing to some of the DxD characters. There could be a lot of cultural exchange and some tense moments as they figure out how to co - exist and whether they can trust each other.
The Gryffindor characters from Harry Potter like Harry himself would probably be very bold and upfront when interacting with the characters in Highschool DxD. They might immediately jump into helping with any dangerous situations. Hermione, with her vast knowledge, could start analyzing the different powers and hierarchies in the DxD world. And Ron might be a bit more cautious but still curious.
Well, characters like Naruto, with his friendly and determined nature, would likely befriend some of the Highschool DxD characters quickly. He might be curious about the different species in their world. And characters like Rias from Highschool DxD would probably be intrigued by Naruto's strong will and his ability to never give up, which is somewhat similar to the way devils in their world pursue power.
The female characters from Highschool DxD, like Rias, would be intrigued by the unique personalities of the Naruto characters. Rias might see potential in some of them to join her peerage. And the Naruto girls, like Sakura, would be a bit shocked at first by the more revealing outfits and flirty nature of some of the Highschool DxD characters. But over time, they would bond over things like protecting their friends and the school. The Naruto boys would respect the power of the Highschool DxD devils and might even try to incorporate some of their fighting strategies into their own ninja combat styles.
Kakashi would be very observant. He'd be quickly analyzing the powers and social structures in The Highschool of DxD. He might take on a mentoring role for some of the younger characters in both worlds. If there were any conflicts, he'd use his wisdom and combat skills to try and resolve them. And he could also learn from the more experienced characters in The Highschool of DxD, like Sirzechs. This exchange of knowledge and skills between the two groups of characters could create a rich and engaging fanfiction story.
The characters from Assassin could teach the Naruto characters some new stealth techniques. For instance, Ezio's parkour skills could be very useful for Naruto ninjas to move around more quickly and quietly. In Highschool DxD, the assassins could also help the devils in their battles by using their assassination skills to take out enemies without being noticed. And Naruto characters like Naruto himself could teach the others about the importance of friendship and never giving up, which could inspire the Highschool DxD characters.
The characters would likely start off being cautious of each other. For instance, the devils in Highschool DxD might be wary of the mages from Fairy Tail as they have different power sources. However, as they get to know each other, they could start to learn from one another. Gray could teach some of the Highschool DxD characters about his ice - making skills, while Issei could show the Fairy Tail members some of his unique devil techniques.
Well, in a crossover, the power systems would be quite interesting to combine. The devils in Highschool DxD have their own demonic powers which are often based on their individual abilities and their Sacred Gears. In Naruto, chakra is the main power source. If a devil were to enter the Naruto world, they might find that their powers are either enhanced or restricted by the presence of chakra. For instance, a devil's teleportation ability might be affected by the flow of chakra in the area. On the other hand, a ninja with high chakra control could potentially learn to manipulate the energy within a Sacred Gear, if they were to somehow obtain one. This could lead to new and unique power combinations that haven't been seen in either universe before.
Given Naruto's status as a yokai, his interactions with the Highschool DxD characters would be complex. He could be a source of mystery to them. With the perverted Issei, Naruto might find his behavior a bit off - putting at first but would gradually understand his character. When it comes to the more powerful characters like Sirzechs, Naruto would show respect but also not be intimidated. He could also form a sort of rivalry with some of the more combat - oriented characters, like Kiba, as they compete to see who is stronger in different types of battles, whether it's a one - on - one fight or a group battle against a common enemy.