He might combine the Chidori with his Sage Mode. In Sage Mode, Naruto has enhanced senses and strength. Adding the Chidori to that would make it an extremely powerful attack. He could use the precise and fast - paced nature of the Chidori while being in Sage Mode, which would give him better accuracy and more power behind the jutsu.
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.
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 the fanfic, Naruto could use the Chidori to save his friends who are trapped by an enemy's powerful jutsu. Since the Chidori is a very fast - moving and piercing attack, he could break through the barriers set up by the enemy. He might also face some internal struggle as using the Chidori goes against his normal style of ninjutsu.
One possible plot could be that Naruto discovers the Chidori technique while training in a secret area. Maybe he stumbles upon some old scrolls left by Kakashi. He then has to train hard to master it, facing difficulties like controlling the lightning chakra. As he progresses, he combines it with his own unique Rasengan, creating a new and powerful jutsu.
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 a fanfic where Naruto knows the Chidori, it could change the power dynamics in battles significantly. Naruto's already vast chakra reserves combined with the piercing and fast - acting nature of the Chidori would make him an even more formidable opponent. He could use it in close - quarter combat situations, perhaps integrating it with his Shadow Clone Jutsu in creative ways. For example, he could have clones perform the Chidori from different angles, catching his enemies off - guard.
It would make him more versatile. He's known for his Rasengan, but using the Chidori would show that he can adapt other powerful techniques. This could make him seem more of a prodigy, as the Chidori is a difficult technique.
Well, he might start with intense training sessions. Maybe he observes Kakashi closely for the Chidori, and for the Rasengan, he practices over and over again, gradually getting the hang of the chakra control required.
One way the Sharingan is portrayed differently in Naruto fanfics is through enhanced powers. In some fanfics, the Sharingan might have the ability to control time or space, which is not in the original series. This is to make the story more unique and engaging.
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.