Well, 'natsu king of fairy tail fanfiction' could potentially be about Natsu being in a position of great power or leadership within the Fairy Tail universe in the context of fan - created stories. Maybe it explores his new abilities, his relationships with other characters when he has this 'king - like' status.
In this fanfiction, perhaps Natsu's return as a 'king' means he has a new level of leadership. He might bring back some lost magic or knowledge that helps Fairy Tail regain its former glory. For example, he could have found a way to defeat an old enemy that was once too powerful for the guild. His return could also stir up emotions among the guild members, like excitement, relief, or even some jealousy from those who might have risen in his absence.
One possible theme could be power and responsibility. As Natsu is in a 'king' role, he has to handle the power that comes with it and the responsibilities towards his friends and the guild.
Natsu is the central figure in this fanfiction. But other characters like Happy, his loyal flying cat companion, will surely play an important role. Makarov, the guild master, would also be a main character as he has to deal with Natsu's return, whether it's a welcome or a bit of a shock to the guild's current state. And don't forget about the villains or antagonists that Natsu and Fairy Tail might face upon his return, they could also be considered main characters in the sense that they drive the plot forward.
Typically, it involves Natsu having some form of romantic or close relationships with multiple characters, creating a harem - like scenario in the Fairy Tail world. There's often a focus on adventure as well, since Fairy Tail is known for its action - packed adventures.
Yes, in a lot of Fairy Tail fanfiction, Natsu can be overpowered. Writers often like to amp up his powers for more exciting storylines. For example, they might give him new fire - based abilities or make his existing ones even stronger to defeat more powerful foes.
In fanfiction, Natsu's age can vary greatly. Some authors might keep him at his canonical age from the original Fairy Tail series, which is around 17 - 18 years old at the start. However, in alternate universe fanfictions, he could be older or younger depending on the plot. For example, in a time - travel based fanfic, he could be much older if the story takes place far into the future or much younger if it goes back to his childhood days.
Often, it could be because of a false accusation. Maybe someone framed Natsu for a crime he didn't commit, like stealing a powerful magical artifact from the guild. So, to maintain peace and order, the guild leaders had no choice but to banish him.
Lucy could be a main character. She was always close to Natsu in the original Fairy Tail. So when Natsu returns as an 'ex' and meets the guild again, she would likely play a big role in how he is received and in the development of the story.
One possible aspect of a Fairy Tail Natsu and Tartaros fanfiction could be Natsu's battle against the powerful foes in Tartaros. He might face new and terrifying enemies that test his limits. His dragon slayer magic would be put to the extreme, and perhaps he discovers new powers along the way.