Another way to blend the cultures is through their forms of combat. The ninja way of fighting in Naruto, with its emphasis on stealth, agility, and various jutsu, can be compared and contrasted with the more brute - force and magical combat in High School DxD. Characters could learn from each other, like a devil learning Naruto's shadow clone jutsu and using it in their battles. This would not only blend the combat cultures but also create new and exciting battle scenarios.
Naruto and Night Elf fanfiction can blend cultures by having characters from both worlds interact. For instance, Naruto's love for ramen could be introduced to the Night Elves, and in return, the Night Elves could teach Naruto about their herbal medicine. This simple exchange of food and knowledge starts to blend the two cultures.
It blends the Japanese - influenced ninja culture from Naruto with the religious and cultural elements of Christianity represented by Jesus. For instance, Naruto's training and his pursuit of becoming Hokage could be paralleled with Jesus' journey of spreading his teachings.
One way would be through power systems. Naruto's chakra could be related to the magic or power in High School DxD. The fox yokai part could be used to explain some of the more mysterious powers. For example, Naruto's fox - like speed and strength could be seen as yokai - like abilities in the High School DxD world.
Well, one way it could blend is by having Naruto's ninja skills incorporated into the High School DxD world. Maybe Naruto could use his shadow clone jutsu to create diversions during the Rating Games in DxD. The Ten Tails' power could be a major plot device, like a powerful force that both sides in DxD are trying to either control or prevent from being controlled. For example, some of the devils in DxD might see the Ten Tails as a way to gain ultimate power over the other factions.
One way is through the power systems. Naruto's chakra could interact with the magic and powers in High School DxD. For instance, a character from High School DxD might be fascinated by Naruto's ability to use chakra and it could be a starting point for a relationship in the mass harem. Another aspect could be the cultures. The shinobi culture of Naruto's world is very different from the high school and supernatural culture of High School DxD. This contrast could create interesting situations in the fanfiction.
A possible blend in the fanfiction could be through a magical or technological device. Maybe a scientist in Highschool DxD creates a device that can open portals to other universes, and Naruto's world is one of the destinations. When Naruto arrives, he discovers that there are elements related to Beelzebub there. The device could malfunction and start to merge the three universes in unexpected ways. This would force the characters to adapt to the new situation, with Naruto using his ninja training to survive, the Highschool DxD characters using their social and magical skills, and those related to Beelzebub using their demonic powers to deal with the chaos.
If Naruto had Kyuubi's power in the High School DxD universe, things would be chaotic at first. His presence would be a shock to the different factions. The devils would likely try to either recruit him or eliminate him. But Naruto, with his strong will and Kyuubi's power, could form new alliances. He could teach the students at the school some of his ninja ways and in turn learn about the magic and powers in that world. His Kyuubi - enhanced abilities would make him a formidable opponent in the Rating Games.
Another approach is to mix the power systems. In fanfiction, the chakra from Naruto could be related to the power of the devils or other beings in High School DxD. For instance, the tailed - beast chakra could be equivalent to a powerful devil's power source. Characters from both universes could then try to learn about and utilize the other's power system. This would create a lot of interesting scenarios where they have to train together or compete to see who has the stronger power.
One way to combine them could be by having Naruto characters enter the world of High School DxD. For example, Naruto with his determination and unique abilities could interact with the devils and other supernatural beings in the DxD world. Maybe he'd form an unlikely alliance or even compete in the Rating Games.
Also, in terms of character relationships, a fanfiction might pair characters from both series in unexpected ways. Maybe a character from Naruto forms an alliance with a devil in High School DxD against a common enemy. This could lead to interesting dynamics and development of new storylines.