They could be a tool for a hero in the fanfiction. A wizard inventor might use nanites to create a new type of magical device. These nanites could be programmed to perform specific tasks like detecting dark magic in the air or helping to heal magical creatures. This would give the hero an edge in their adventures against the forces of evil in the wizarding world.
Nanites could also be a mystery element in the plot. A strange phenomenon starts occurring in the wizarding world where things seem to be malfunctioning at a microscopic level. It turns out to be nanites that have somehow made their way into the magical realm, perhaps through a portal or a misfired spell. The characters then have to figure out where they came from, what they do, and how to stop or control them.
It could be a villain. Maybe it's been corrupted by dark magic and is out to attack students at Hogwarts.
In the fanfiction, Naruto's immortality could make him a key figure in resolving long - standing conflicts. He has the time and the power to study both the wizarding and ninja worlds deeply. So he could use his knowledge to find solutions to problems that have been plaguing the wizarding world for ages, like the fight between pure - bloods and half - bloods or the threat of dark wizards. His presence would bring a new dynamic to the story as he doesn't have the same limitations as the regular Harry Potter characters in terms of lifespan and the type of power he wields.
She could play the role of a new friend. For example, she might be a transfer student from a different wizarding school who befriends Harry and helps him in his fight against the dark forces. Maybe she has some unique magical abilities that give an edge in battles.
He could be a mentor. Since he's immortal, he has a vast amount of knowledge and experience. He could teach young heroes or anti - heroes about the value of life and how to use their powers responsibly. For example, he could guide Robin on how to be more strategic in combat, sharing his own experiences from fighting Voldemort.
Another concept could be that the nanites are a new form of magical creature. They could have their own language and culture, and wizards and witches would have to learn how to communicate with them in order to use their powers.
Often, the main characters are still Harry, Hermione, and Ron. But with the addition of the nanites, their personalities and abilities might change. For instance, Harry could use the nanites to better understand Voldemort's magic.
She could play a protective role towards Harry. Since she's older, she might feel a strong sense of responsibility for her younger brother. For instance, she could be the one who first discovers some of the secrets about Voldemort's return and warns Harry.
He could be an antagonist. Maybe he tries to steal magical artifacts from Hogwarts for his own gain.
She could be a powerful witch. Maybe she's a long - lost relative of Minerva McGonagall, and she comes to Hogwarts to teach a new and unique subject. For example, a subject about ancient magic spells that have been forgotten over time.
The Black Magic Gundam could be a protector. Maybe it was created by an ancient wizard to safeguard the wizarding world from a great threat that was foreseen. In the fanfiction, it could be reactivated to fight against a new dark force that the normal spells and magic of the wizards can't handle.