Naruto might be initially excited. He's always eager to learn new and powerful jutsu, and the Chidori is a very cool and strong one. He probably can't wait to start training and show off to his friends once he masters it.
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.
Naruto's fighting style could become more versatile. He already has a wide range of skills, and adding the Chidori gives him another option. He can now combine it with his shadow clones. For example, he could send clones to distract the enemy while he sneaks in with the Chidori.
The main characters are obviously Kakashi and Naruto. Kakashi is the experienced and somewhat mysterious ninja who has a lot to teach. Naruto is the eager - to - learn protagonist who is always looking to improve his skills.
Well, in some 'kakashi teaches naruto fanfiction', there might be a plotline where Kakashi teaches Naruto how to better control his chakra. This could involve some really intense training sessions deep in the forest. Also, Kakashi could be teaching Naruto about the art of stealth and infiltration, skills that Naruto doesn't have much experience with but are crucial for a ninja.
In a more creative fanfic, an ancient ninja who was the originator of the Chidori technique could appear. This ninja could be brought back to life through some sort of magic or jutsu. He sees Naruto's pure heart and decides to pass on the Chidori knowledge to him, believing Naruto will use it for good.
In fanfiction, Naruto creating Chidori could be possible through some creative plot devices. Maybe he was taught by Sasuke in an alternate universe where they teamed up earlier. Or perhaps he discovered a scroll that had the knowledge of Chidori and was able to learn it on his own with his determination and quick - learning ability.
In many Naruto fanfictions, the Chidori - Rasengan combo is often portrayed as an extremely powerful and unique move. It combines the piercing nature of the Chidori with the rotational and explosive force of the Rasengan. Some fanfictions might have Naruto or Sasuke (or both in some cases) creating this combo during a crucial battle against a powerful enemy, like a new Akatsuki member or a rogue ninja from another village. This combo is usually described in great detail, with the lightning - chakra of the Chidori surrounding and enhancing the Rasengan, making it not only more destructive but also having an added effect like paralysis due to the electricity.
Sasuke could be Naruto's teacher. Since Sasuke is a master of the Chidori, he might decide to teach Naruto as a way to make Naruto a more formidable ally. They have a complex relationship, and this could be a way to strengthen their bond.
One possible scenario could be that Naruto learns the Chidori from Sasuke in a moment of truce. Sasuke, realizing Naruto's determination to become stronger, decides to teach him this powerful jutsu. Another could be that Naruto discovers a scroll that contains the secrets of the Chidori and through his own hard work and study, he manages to master it. Or perhaps, a new character appears who has knowledge of the Chidori and trains Naruto in it as part of a greater plan to defeat a common enemy.