In this fanfiction idea, Naruto being Rias' younger adopted brother would bring a lot of chaos and new possibilities. Naruto is used to a world full of shinobi, where chakra is the main power source. In the DxD world, there's magic and demonic powers. His presence would lead to some interesting experiments and training sessions. Maybe they would try to combine chakra and magic. Also, Naruto's past of being an outcast in his own village could make him more empathetic towards some of the characters in DxD who are also seen as different. This could lead to some heart - warming moments of acceptance and friendship.
If Naruto is Rias' younger adopted brother, it would completely shift the power dynamics. Naruto has the power of the Nine - Tails, which is an extremely powerful force. This could make Rias' group even more intimidating. In terms of relationships, Naruto's friendly and outgoing nature would probably attract a lot of new friends within the High School DxD setting. He might also get into some funny cultural clashes, like when his ninja values meet the more demon - centric values of the DxD world.
Well, in this fanfic scenario, Naruto's ninja skills could be a huge asset in the High School DxD world. He might introduce new combat styles and strategies. For example, his shadow clone jutsu could be used in various battles or for pranks. Also, his strong sense of justice would likely influence Rias and her peerage. He could help them make more morally upright decisions, and his experience with facing powerful enemies in the Naruto universe would give them new perspectives on handling threats in their own world.
Well, if Naruto were Rias' twin brother, it would completely change both storylines. In Naruto's world, his new family connection to the Gremory family in High School DxD might introduce devilish powers and politics into the Hidden Leaf Village. This could lead to new alliances and rivalries. For example, the Akatsuki might view Naruto differently, seeing him as a potential link to a powerful devil family. In High School DxD, the devils might be more involved in the affairs of the ninja world, perhaps trying to gain access to unique ninja techniques. It would also change Naruto's and Rias' characters. Naruto might grow up with a different sense of self, having a devil heritage, and Rias would have a strong connection to the ninja world through her brother.
Another possibility is that there is a tournament that spans multiple universes. Naruto is selected to represent his world, and Rias volunteers or is chosen to represent the High School DxD world. They meet at the tournament grounds. At first, they might be a bit suspicious of each other, but as they see each other's skills and determination in the battles, they start to respect and eventually become friends, working together to win the tournament for their respective worlds.
In a fanfiction where Naruto is Rias' brother, the Naruto storyline would be altered significantly. Naruto's nature as a person might change due to the influence of the devil society. He may become more sly or strategic in the way devils are. His fighting style could incorporate more magic - like elements from the DxD world. His backstory would now involve being part of a devil family. His relationships with his friends in the Naruto world would be less prominent as he'd be more involved with the devils. For example, instead of going on missions in the ninja world, he'd be involved in devil - related tasks to protect his sister and their family's status.
One possible idea for this fanfiction could be Naruto being transported to the world of High School DxD. He might end up attending the same school as Rias. Given Naruto's strong sense of justice and his combat skills, he could quickly become involved in the supernatural battles and power struggles in that world. He might also form an interesting relationship with Rias, perhaps starting as friends and gradually developing into something more as they face various challenges together.
I'm not entirely sure if there is such a specific fanfiction. There are thousands of fanfictions out there, and while the concept seems interesting, it could be a relatively niche idea. You might have to search through various fanfiction websites dedicated to both Naruto and the series Rias is from. Maybe start with popular ones like FanFiction.net or Archive of Our Own and use relevant search terms to see if you can find it.
There could be a storyline where Naruto is summoned to the High School DxD world by some ancient magic. He is seen as a powerful ally or a threat depending on who you ask. Rias takes it upon herself to figure out Naruto's intentions. As she gets to know him, she realizes that his values of friendship and protecting the weak are similar to her own. Together, they start a journey to stop a dark force that is rising in the DxD world, with Naruto teaching the devils some ninja techniques along the way.
A great plot could be a tournament - style story in the 'Naruto x Rias High School DxD' fanfiction. The tournament could be a mix of ninja and devil skills. Naruto enters representing his ninja heritage and Rias enters on behalf of the devils. Along the way, they have to face opponents from different factions. As they progress, they start to understand each other better and develop a deeper bond. Naruto's determination to win for the sake of his new friends in the DxD world and Rias's desire to prove the strength of the devils would drive the story forward, and their combined efforts could lead to an unexpected victory.
Well, one possible plot could be Naruto growing up in the world where Rias lives. He might struggle to fit in at first because of his different upbringing in the Naruto universe. But then, he could use his ninja skills and strong will to protect his sister Rias and her friends. He could also introduce some new ninja - like elements to their world, like new combat techniques or ways of training.
The plot could also be centered on a mystery related to their family. The brother of Rias discovers some secrets about their family's past that put them both in danger. He then has to work with Rias to uncover the truth and stop whoever is trying to use their family secrets against them. This could involve battles, political intrigue within the Devil world, and self - discovery for both of them.
One way could be through the power system. The EMS (Eternal Mangekyou Sharingan) from Naruto could be a unique power that a character in the High School DxD world acquires. Maybe a transfer student from a hidden ninja village arrives at the high school and has to keep their EMS a secret while dealing with the devils and angels in the school. This could lead to some interesting battles and interactions as the powers of the EMS, like the ability to use powerful jutsus, contrast with the magic and abilities of the High School DxD characters.