Perhaps in this fanfiction, Naruto has lost his way in his own world and somehow ends up in Rias' realm. Rias, being kind - hearted, adopts him. Naruto would have to adapt to a whole new set of rules and powers. He might face challenges from other groups who are suspicious of this new addition, but with his ninja spirit, he overcomes them.
In the 'naruto adopted by rias fanfiction', it could start with Naruto being in a vulnerable state, maybe after a great battle. Rias discovers him and decides to take him in. As he becomes part of her world, he has to deal with the complex social structure. He might also form new bonds with the characters around Rias. His chakra abilities could be combined with the magic in Rias' world in some really interesting ways.
One possible plot could be that Naruto and Rias, through some magical or unexpected circumstances, find themselves in a relationship. Their pregnancy could then bring about various challenges. For example, they might face opposition from their respective worlds. Naruto's world of ninjas might not understand his relationship with Rias from a different realm, and vice versa. Their friends and allies would have different reactions, some being supportive while others being skeptical. They would also have to deal with the practical aspects of preparing for a baby, like finding a safe place to live and ensuring the child's future in two very different and complex worlds.
In such a fanfiction, perhaps Naruto is in a new world where Rias, for some reason, completely ignores him. Maybe it could lead to Naruto feeling isolated and having to find his own way in this strange new place. He might start training alone and discover new powers out of his need to prove himself despite Rias's neglect.
Well, it could start with Naruto somehow ending up in the world of High School DxD. Rias might discover Naruto and see his potential, then make him her familiar. The plot could involve Naruto learning about the devil society and using his ninja skills to protect Rias and her peerage.
One possibility is that Naruto is summoned to Rias' world through some sort of magical ritual gone wrong. Once there, he forms an unlikely alliance with Rias. Naruto's chakra - based powers could be a great asset to Rias' team. They might start training together, with Naruto teaching the devils about chakra control and Rias showing Naruto some of the unique magic in her world.
One possible plot could be that Naruto, as Rias's brother, brings his ninja skills to the world of High School DxD. He might use his jutsu to protect Rias and her peerage from various threats, like the devils from other factions or rogue exorcists. And along the way, he could also teach some of his ninja techniques to the members of Rias's peerage.
Well, one possible plot could be that Naruto, as the son of Rias, discovers his unique heritage and has to deal with the expectations that come with it. He might struggle to balance his ninja skills with the devil - like powers he inherits from Rias. Maybe he uses his Naruto - like determination to bridge the gap between the ninja world and the world of devils.
The plot could involve Naruto using his knowledge of chakra to diagnose Rias' brother's illness. He might discover that it's not a normal sickness but something related to the supernatural nature of their world. For example, his chakra flow could be disrupted by a dark magic spell.
In a fanfiction where Naruto is adopted by Rias, there would be a significant cultural clash at first. Naruto comes from a world of shinobi where loyalty to the village is key, while Rias's world has its own set of values regarding loyalty to the devil clan. However, Naruto's growth potential is huge. His rasengan could potentially be modified with the magic in Rias's world. He could also teach some of his ninja training methods to the members of Rias's peerage, enhancing their combat capabilities. And his experience with fighting powerful enemies in his own world would give him an advantage when dealing with threats in Rias's world.
The plot might involve Naruto trying to adapt to the new environment of being related to Rias. Since he has his own strong sense of justice from his ninja world, he could conflict with some of the more underhanded tactics in Rias' world. But in the end, they work together to overcome difficulties. For example, when facing a powerful enemy that neither of them could handle alone, they combine Naruto's ninjutsu and Rias' devil powers to defeat it.
Well, perhaps Rias, for some reason, abandons Naruto in a dangerous situation where he is left to die. Maybe there's a conflict of interests or a misunderstanding between them. It could be that Rias has to make a tough choice that unfortunately leaves Naruto in a life - threatening state.