As I haven't read it, I can't say for sure. But based on the title, the main character is likely to be 'the man of the azure'.
Given the title 'the man of the azure fanfiction', one would assume that the main character is this 'man of the azure'. However, without reading the fanfiction, we don't know if there are other important characters who might share the spotlight or if there are twists that make the main character not exactly who we expect at first glance. It could be that there is a group of characters and the 'man of the azure' is the central figure among them, leading the plot forward through his actions and decisions.
I'm not entirely sure as I haven't read it specifically. But generally, a fanfiction with 'the man of the azure' might be about a male character who has some sort of connection to the color azure. It could be about his adventures, his personality, or his relationships in a fictional world created by the fanfiction writer.
The main character could also be a new character created specifically for the fanfiction. This new character might be someone who is deeply affected by the will of the single man, and the story could be told from their perspective as they navigate the consequences of that will.
As we don't know the details of 'the man story', the main character is simply 'the man' in question.
It could be a simple farmer who discovers an ancient spear and then his life changes. He might be an ordinary man thrust into extraordinary circumstances because of the spear.
It could be Tony Stark's daughter. She might have inherited her father's genius and his sense of justice. Growing up in the shadow of her father, she decides to take on the mantle of Iron Man to prove herself and carry on his legacy.
Perhaps a forward - thinking businessman. He might be the one who sees the potential in new technologies and invests heavily in them. He then uses his business acumen to spread these technologies across the fictional land, making him the catalyst for the industrial revolution. For example, he could be the first to mass - produce a new type of machinery, which then becomes the cornerstone of many industries.
Sasuke could be a likely candidate. He has always had a bit of a lone - wolf streak in the original series. He might decide to form his own 'one man team' to pursue his own goals, like finding out more about the Uchiha clan and getting revenge in his own way without depending on others too much.
Mega Man Zero could also be the main character if the story focuses on his adventure in the Naruto world. He would be the outsider, having to learn about chakra, ninja clans, and the political structure of the Naruto world. His combat skills and sense of justice would play a big role in how he navigates this new and strange world.
Since I don't know the exact 'pickle man story', I can't say for sure. But it's likely the main character is the pickle man himself.
I'm not sure as I haven't read the specific 'the mystery man novel'. But usually in mystery novels, the main character could be a detective or an ordinary person who gets involved in mysterious events.