Well, let's consider Kiba from High School DxD. He's a proud devil with his own set of skills. If Naruto Juubi was in the fanfiction, Kiba might be a bit jealous of its power at first. He might try to prove himself by competing with Naruto Juubi in some way. Xenovia, with her strong sense of justice, could have an interesting relationship. She might see Naruto Juubi as an unknown entity and be on guard, but also be curious to see if it has good intentions. Naruto Juubi, coming from the Naruto universe, might be confused by the different social norms in High School DxD. This could lead to some comical interactions with characters like Asia, who is very kind - she might try to befriend Naruto Juubi and explain the ways of their world.
In a High School DxD fanfiction with Naruto Juubi, the character interactions would be diverse. The devils in the student council, like Sona, would likely approach Naruto Juubi from a strategic point of view. They would want to know how this new power could be used to their advantage or if it would disrupt their plans. The fallen angels might see Naruto Juubi as a wildcard that could change the power struggle among the different factions. Characters like Vali, who are always looking for strong opponents, would be eager to test their skills against Naruto Juubi. And Naruto Juubi's own personality, if it retained any from the Naruto series, would also play a role. If it was still a bit of a loner like in Naruto at times, it might initially keep its distance from the others, but as the story progresses, form unique bonds with certain characters.
Rias would probably be very interested in Naruto's Hiraishin. She might see it as a powerful tool for her peerage. Issei, on the other hand, would be both amazed and a bit envious. He might try to challenge Naruto to a friendly spar to see how it works. And Akeno would likely be intrigued by Naruto himself, with the added allure of his unique jutsu.
One possible fanfic could be about Naruto being transferred to the High School DxD universe and his encounter with the Juubi there. Maybe he has to team up with the characters from High School DxD to deal with the threat of the Juubi. For example, Naruto's unique abilities like the Rasengan and Shadow Clone Jutsu could be a great asset in battles within this new universe.
Naruto and Issei would be really interesting. Naruto, with his positive and determined attitude, would contrast with Issei's more pervy and hot - blooded nature. They could learn a lot from each other. Another interesting interaction could be Naruto and Sirzechs. Sirzechs, as a powerful devil king, would be intrigued by Naruto's power source, the Juubi. And Naruto would be interested in Sirzechs' leadership and power management in the devil world.
Well, if Naruto Juubi was in High School DxD fanfiction, the storyline would change drastically. For one, the power dynamics would be completely different. Naruto Juubi is extremely powerful, and in the High School DxD world which already has a complex power system, it would disrupt the existing balance. The characters in High School DxD would have to adapt to this new, overpowering force. Maybe some would try to ally with it, while others would see it as a threat. Also, the cultural and personality differences between the Naruto universe and High School DxD would create interesting interactions. Naruto Juubi's values from the Naruto world might clash or blend with the more modern and somewhat hedonistic values of the High School DxD characters.
Naruto might also interact with the Juubi on a more strategic level. He could plan with the characters from High School DxD to contain the Juubi first. For example, using the barriers and spells available in the DxD world along with his own shadow clone jutsu to surround the Juubi. Then, they could work on finding a more permanent solution, like using some ancient magic from the DxD universe combined with Naruto's sealing jutsu.
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.
Naruto and Ravel might start off as strangers. Naruto would be the curious outsider, and Ravel would be intrigued by his different appearance and powers. Then, Naruto could interact with other DxD characters. For example, he might have some friendly competitions with Issei. As the harem forms, Naruto would have to balance his relationships with different girls. He might have deep conversations with Ravel about their different worlds and values.
Goku could have some interesting interactions. He might befriend Issei for his determination. Goku, being a pure - hearted fighter, would probably respect Issei's will to get stronger. He could also have friendly rivalries with some of the stronger devils or angels, challenging them to friendly spars to test their strength.
Sakura could interact with the teachers in Akatsuki High School. Maybe she has a really strict teacher who she has to work hard to impress, or a really kind teacher who becomes her mentor.
A crossover might involve power - up scenarios. The Hound from the fanfiction could potentially gain some of Naruto's chakra or learn his techniques. In the High School DxD universe, this new power could disrupt the existing power balance. Also, the story could focus on the relationships between the characters. Naruto is known for his strong bonds with his friends, and this could be contrasted or integrated with the relationships in High School DxD, like the complex relationships between the devils, angels, and fallen angels.