In such fanfics, you might find Naruto dealing with the expectations and responsibilities of being a ninja at a younger age. They might also play with the idea of time travel or alternate timelines, adding an extra layer of excitement. The character development can take unexpected turns too.
He might develop new relationships. Since he's de - aged, he could make friends with people who he didn't interact much with before. For example, he could befriend some of the younger ninjas in a different way and learn from them too. This could change his perspective on teamwork and friendship.
A possible plot is that de - aged Naruto is sent to a parallel universe where things are very different in the ninja world. He has to adapt quickly and find a way back to his own universe while being a child, which would be full of challenges and new discoveries.
I'm not entirely sure as 'after era un fanfic' is a rather unclear phrase. 'Fanfic' stands for fan fiction, which is a fictional story written by fans of a particular work. But 'after era' is rather strange. It could potentially mean something like 'after a certain era' in the context of the fanfic, but without more context it's hard to be precise.
The Legend of Uzumaki Hiroto was a derivative work of Naruto, which told the story of Uzumaki Hiroto's growth and the stories of other characters. Uzumaki Boto Legend was different from the original Naruto Naruto Shimbun Legend, so it was considered an independent manga.
Let's say there was a popular fanfic about a superhero. 'After era un fanfic', there could be a new wave of fan - made art inspired by that fanfic. So, the fanfic came first, and then, after it, there was this new creative output in the form of art.