The plot might involve Tenzo seeing Naruto's potential but also his flaws. So he decides to train Naruto not only in physical and ninjutsu skills but also in mental strength. Tenzo could share his own experiences of dealing with the dark side of the ninja world, helping Naruto to better understand the importance of balance and self - control. This training could be a turning point for Naruto, making him more mature and a more formidable ninja.
Obviously, Naruto and Tenzo would be the main characters. Naruto, as the one being trained, is the protagonist of the Naruto series. And Tenzo, with his unique skills, is the trainer in this fanfic.
She could be someone with a special bloodline or ability. Maybe she has a unique form of chakra that gives her certain powers. In the context of training Naruto, her skills and knowledge are what make her important. She could be a mysterious figure who has been observing Naruto for a while and decides to take him under her wing to help him reach his full potential. For instance, she might have the ability to see the latent potential in others and wants to shape Naruto into a great ninja not just for his own sake, but also for the greater good of the ninja world.
It could lead to Naruto becoming even stronger and more skilled than in the original story. Jiraiya's training methods might unlock new powers for him.
In a 'naruto trained by ruby' fanfic, perhaps Ruby could introduce Naruto to some unique combat styles. Maybe Ruby has her own set of skills like some kind of magic or special weapon techniques. She could teach Naruto how to combine his chakra with these new elements. For example, if Ruby has some sort of elemental magic, Naruto could learn to infuse his Rasengan with that magic for a more powerful attack.
A 'naruto trained by orochimaru fanfic' might have Naruto delving deeper into the secrets of the Sharingan. Orochimaru has always been interested in the Uchiha's power. So Naruto, under his training, could be exposed to knowledge about the Sharingan and its potential. This might lead to some interesting power - ups for Naruto, but also put him in the crosshairs of other powerful ninja who are also interested in the Sharingan's secrets.
Well, it could be about Naruto getting special training from Sarutobi in stealth. Maybe Sarutobi teaches Naruto some ancient jutsu that only he knows. This would give Naruto an edge in battles and make him more respected in the village.
In a 'naruto trained by selphe fanfic', perhaps Selphe comes from a different ninja clan with ancient techniques. She could teach Naruto how to combine his existing Rasengan technique with her clan's special chakra manipulation. This would make Naruto's attacks even more powerful and unpredictable. Also, Selphe might train Naruto in mental discipline, which would help him better handle the stress of battles and his role as a future Hokage.
Well, it could be that in this fanfic, Kakashi discovers a new potential in Naruto. He might train Naruto in some ancient and forgotten ninja arts. This would set Naruto apart from his canon self. Also, their relationship could be explored more deeply, like Kakashi becoming a father - figure to Naruto, and this emotional bond could influence Naruto's growth as a ninja.