Well, perhaps the retired shinobi has some secrets from his past. When he adopts Naruto, he starts to pass on these hidden techniques and knowledge. Along the way, Naruto might also help the retired shinobi come to terms with his own past traumas or unfulfilled dreams. As a result, they both grow and Naruto becomes a more well - rounded shinobi under this new mentorship.
In this fanfic, the retired shinobi might adopt Naruto because he realizes Naruto is being ostracized by the village. He takes Naruto away from the village for a while to train him in isolation. During this time, Naruto learns about the retired shinobi's adventures in the past, which inspire him. When they return to the village, Naruto is a changed and much more powerful shinobi, ready to face the challenges that await him with new confidence.
Perhaps it's a shinobi who has retired after a long and eventful career. He could be someone who has seen the darker side of the shinobi world and wants to make sure Naruto doesn't go down the wrong path. He might have been a wandering shinobi who finally settles down with Naruto. For example, he could be a shinobi from a different village who has a unique set of skills to teach Naruto.
One interesting plotline could be Naruto adjusting to civilian life after retiring. He might struggle with the boredom of not having the constant action and purpose he had as a shinobi. Another could be him mentoring the next generation in a more laid - back way, passing on his wisdom without the pressure of active duty.
Obviously, Naruto is one of the main characters since it's about his retired life as a shinobi. Sakura could also be a main character, perhaps she still works as a medical ninja and has a different relationship with Naruto now that he's retired. Another could be Boruto, Naruto's son, as he would be affected by his father's retired status.
One possible plot could be Naruto dealing with the boredom of retirement. He might try to find new hobbies like gardening in Konoha. Maybe he starts teaching some young ninja in an unofficial way, passing on his unique skills and experiences.
The fanfic could also focus on the personal lives of the characters. Naruto might finally have time to focus on his relationship with Hinata. There could be stories about how they build their family, and how Naruto balances his role as a family man with his duties as a hero of the ninja world. At the same time, other characters like Sasuke could also be exploring their new identities in a post - war world, trying to find their place and purpose.
Perhaps the plot could involve Sarutobi protecting Naruto from the more malicious elements in the village. He could use his influence to ensure Naruto has a normal childhood, or as normal as it can be for a jinchuriki. Naruto might also inherit some of Sarutobi's wisdom and leadership skills, which would be important for his future development.
Well, it could be about Naruto growing up under Kurenai's care and learning different jutsu from her. Maybe he also forms a close bond with her students like Hinata and Kiba.
Well, it could be about Naruto being taken in by Dante. Maybe Dante sees Naruto's potential and decides to train him in his own unique combat styles. This could lead to Naruto having new powers and abilities that combine his own ninja skills with Dante's devil - may - cry - like powers.
Well, it could be that Naruto is somehow transported to the Avatar world and Azula, seeing his potential or maybe out of some self - serving reasons, decides to adopt him. Naruto might bring his ninja skills and his never - give - up attitude to this new world. He could start learning about bending and in turn teach Azula some of his ninja tricks.
One possible plot twist could be that the real enemy is secretly manipulating the Shinobi Alliance to fight Naruto. So Naruto has to not only defend himself but also figure out who is behind it all. Another could be that Naruto discovers a hidden power within himself during the fight that changes the course of the battle.