It would blend the worlds by character interactions. Naruto could make friends with some of the Highschool DxD characters. He might use the Susanoo to protect them in dangerous situations. The fanfic could also introduce new story arcs based on the combination. For example, a new villain could emerge that is interested in Naruto's Susanoo power and wants to use it for their own evil plans in the Highschool DxD world. This would force Naruto and his new friends to work together to stop the villain.
The blending could happen in the form of cultural exchange. Naruto comes from a world with a strong ninja culture. In the fanfiction, this culture could be introduced to the Highschool DxD world. The Susanoo, as a part of Naruto's culture of power, could be a symbol of strength and mystery. Highschool DxD characters might be intrigued by it and try to understand it. At the same time, Naruto could learn about the different cultures in Highschool DxD, like the demon and angel cultures. This exchange could lead to new relationships and story developments in the fanfiction.
One way is through the power system. The Susanoo's power could be compared or combined with the powers in Highschool DxD. Naruto could bring his ninja way of thinking into the Highschool DxD world. For instance, his idea of never giving up could inspire the Highschool DxD characters. And in terms of the world - building, the fanfic could have Naruto's world of ninjas and the Highschool DxD's world of demons and angels co - exist. The Susanoo could be seen as a new and fearsome power in the Highschool DxD world.
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 we consider Naruto and Kunou in a Highschool DxD fanfiction, Naruto could potentially be seen as a rival to some of the more powerful male characters in DxD. His determination and never - give - up attitude would be a contrast to the often more laid - back or self - interested characters in that world. Kunou, on the other hand, might form alliances with some of the female characters, sharing her knowledge of yokai with them and learning about the devils and angels in return.
Well, one way is through character exchanges. Imagine a character from Naruto like Naruto himself ending up in the Highschool DxD universe and meeting Leviathan. He could introduce his ninja skills to that world and also learn about the devil powers. Another way is to have a common enemy. For instance, a new threat that can only be defeated by combining the unique powers from all three, like the Rasengan combined with a Highschool DxD power against an enemy threatening Leviathan.
Often, the storylines blend by having characters from Naruto end up in the Highschool DxD world. For example, Naruto might be summoned there by some sort of magic accident. Then, he has to navigate this new world full of devils, angels, and other supernatural beings while still having his ninja mindset and skills.
It could be a very exciting fanfiction. Imagine Naruto's powerful jutsu combined with the unique elements of Highschool DxD. The Susanoo might be used in battles within the Highschool DxD setting. For example, Naruto could be a transfer student in the Highschool DxD world. His skills and the Susanoo would be a great addition to the existing power dynamics. Maybe he would form an alliance with some of the characters from Highschool DxD and use the Susanoo to fight against common enemies.
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.
One possible fanfiction could be about Naruto somehow ending up in the world of Highschool DxD and meeting Moka. Maybe Naruto's skills and his never - give - up attitude would impress Moka and the other characters. He could teach them some of his ninja techniques, like the Shadow Clone Jutsu, which could be useful in battles against the devils and other supernatural beings in the Highschool DxD world.
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.
A possible way for their worlds to merge in fanfiction is through a reincarnation plot. What if some of the Naruto characters were reincarnated in the Highschool DxD world? Naruto himself could be reborn as a devil or an angel. This would completely change the power balance and relationships in the Highschool DxD world. Rias would have to deal with this new Naruto, who still has his ninja spirit but now has to adapt to the rules and powers of the new world.
One way they can blend in fanfiction is through the characters' personalities. Saitama's laid - back yet extremely powerful personality could contrast with Naruto's determined and growth - oriented one. In Highschool DxD, the characters are often more flamboyant and passionate. You could write a story where they team up to fight a common enemy. Maybe an otherworldly threat that combines the threats from each of their original worlds. Saitama could use his one - punch to quickly take out some of the minions, while Naruto uses his Rasengan and other jutsu, and the Highschool DxD characters use their Sacred Gears and demonic powers.