Maybe Sasuke teaches him the Chidori in a moment of camaraderie. And for the Rasengan, it could be an older and wiser Naruto from the future who travels back in time to teach his younger self.
In many fanfictions, Naruto might master the Rasengan through intense and unique training methods. Maybe he gets some special guidance from an unexpected source, like a hidden shinobi in the village who has a different perspective on chakra control. This person could show Naruto some new ways to focus his chakra, which finally enables him to form the Rasengan successfully.
In some fanfictions, Kakashi could also play a role. He is very knowledgeable and has seen the Rasengan in action. He might offer some tips on chakra control, which is crucial for Naruto to master the Rasengan.
Well, Tsunade could be a great helper. She has extensive knowledge of chakra control and medical ninjutsu. She could teach Naruto how to use his chakra more precisely when creating the Rasengan, perhaps by showing him some medical - ninjutsu - based chakra control techniques that can be applied. Minato, Naruto's father, could also play a role. He was the one who originally created the Rasengan. He could appear in Naruto's dreams or in some sort of time - travel scenario and show Naruto some hidden aspects of the Rasengan creation that he didn't know before. And then there's Sakura. She's become very strong over time. She could use her strength and knowledge to assist Naruto, maybe by creating some sort of training regimen for him to improve his Rasengan creation skills.
I'm not entirely sure specifically as 'annabeth' is often from the Percy Jackson series and 'rasengan' is from Naruto. It could be a fan - created story that combines elements of both universes in some way, perhaps with Annabeth somehow getting involved with the power or concept of the Rasengan.
Well, in some fanfics, Naruto might add elements to the Rasengan through intense training and experimentation. He could study different chakra natures and find ways to combine them with the Rasengan's basic form. For example, he might infuse lightning chakra into it to make it more piercing and fast - like a lightning - enhanced Rasengan.
Sakura. It would be really unexpected as she is mainly known for her medical ninjutsu and physical strength. But if she were to learn the Fire Rasengan, it could show a whole new side of her character. Maybe she'd incorporate her medical knowledge into the technique, like using it in a more precise and less destructive way.
One interesting Naruto Demon Wind Shuriken fanfiction is 'The Power of the Demon Wind Shuriken'. In this story, the author delves deeper into the origin of the Demon Wind Shuriken. It shows how Naruto discovers an ancient scroll that reveals secrets about the shuriken's creation and its hidden powers. The story has great action scenes where Naruto uses the enhanced knowledge of the shuriken to fight powerful enemies. It also explores Naruto's growth as a ninja as he masters new techniques related to the Demon Wind Shuriken.
One idea could be a story where Naruto teaches the shuriken shadow clone jutsu to a new generation of ninja in a post - war Konoha. They then use it in a friendly competition to see who can create the most effective and creative use of the jutsu.