Sure, the Noragami manga is completed. It was a great ride with an ending that wrapped up the plot nicely. If you haven't read it yet, it's worth giving a go.
I'm not sure specifically as there could be many different plots in fanfictions with this title. It might involve Naruto receiving some special power or protection from the Tsukuyomi. Maybe it could be about Naruto being in a unique situation where the Tsukuyomi's influence changes his fate in the Naruto universe.
In fanfics about Naruto's Infinite Tsukuyomi dreams, often the authors explore the deepest desires and fears of the characters. For example, Naruto might dream of a world where there is true and lasting peace in the ninja world, with all the villages united. This could show his innermost longing which is usually overshadowed by his daily battles and struggles.
Noragami is about a minor god named Yato. He wants to have a grand shrine and a lot of followers. He meets a girl named Hiyori who can partly leave her body due to an accident. They get involved in various supernatural events and battles against other spirits and gods. Yato also has a regalia named Yukine who he has to deal with as Yukine has his own growth and problems.