Well, it could be about Mikoto seeing Naruto's lonely situation and deciding to take him in. Maybe she'd teach him some Uchiha techniques and help him grow stronger. She could also introduce him to Sasuke as a brother figure, changing the whole dynamic between Naruto and Sasuke in the Naruto world.
In such a fanfiction, it could be a story full of new possibilities. Mikoto Uchiha, with her kind heart, might offer Naruto the family he always desired. She could teach him some Uchiha techniques secretly, which would make Naruto even more powerful and unique in the ninja world.
Naruto's life would experience a significant shift. With Mikoto Uchiha adopting him, he would be exposed to the Uchiha way of life. He might get to learn about the clan's traditions, which could shape his character in new ways. His living situation would improve, as he'd be in a more stable family environment. In terms of his ninja development, Mikoto could pass on some of her own knowledge or connect him with other Uchiha members who could help him train. This could lead to Naruto having a more diverse set of skills and a different perspective on the ninja world compared to his original story.
Well, it could be that Mikoto is trapped in a dangerous situation like a collapsing building or a genjutsu. Naruto, with his strong will and powerful chakra, breaks the genjutsu or rescues her from the rubble. He might sense her distress using his Sage Mode or his connection to the Nine - Tails' chakra and rush to her aid.
The child could be an orphan from a small, destroyed village that Naruto comes across during one of his missions. This child might have lost their family to a powerful enemy and Naruto feels a sense of responsibility to take them in.
Well, Naruto would face quite a few challenges as Mikoto's father. Firstly, he has his own reputation and duties as a hero of the village. Balancing his time between being a father and fulfilling his village responsibilities would be tough. Secondly, Mikoto is from the Uchiha clan which has a dark history. Naruto would need to make sure Mikoto doesn't get influenced by any negative Uchiha ideologies. He'd also have to deal with the fact that Mikoto might inherit some of the Uchiha's pride and stubbornness, which could lead to clashes between them as she grows up.
In such a fanfiction, Mikoto would likely be very protective of Naruto. As a godmother, she would probably be involved in his upbringing, teaching him things about the ninja world, and maybe even some Uchiha clan secrets if she thought it was necessary for his growth.
Another idea for a fanfiction could revolve around a mission. Naruto, Kushina, and Mikoto are sent on a dangerous mission to retrieve a powerful artifact. Along the way, they face various challenges that test their teamwork. Kushina uses her strong will and Uzumaki chakra to break through barriers, Mikoto uses her Sharingan to detect hidden enemies, and Naruto uses his Rasengan and his never - give - up attitude to keep them going.
Yes, there are likely Naruto Mikoto fanfictions out there. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Naruto Mikoto' and you'll probably find a variety of stories written by fans.