The main characters would likely include the Ultra Guardians themselves. They are probably a group of trainers with special skills or abilities. There could be a leader among them, who is very experienced and has a deep knowledge of Pokemon.
In addition, there could be a villain or a group of villains in the fanfic. These antagonists would constantly try to disrupt the Ultra Guardians' plans and cause chaos in the Pokemon world. They might have their own motives, like trying to gain control over all the powerful Pokemon or seeking revenge on the Guardians for past defeats.
Since I haven't read it, I can't say for sure. But it could be some popular Pokémon from the Altomare region like Latias or Latios.
One interesting storyline could be the discovery of a new and extremely powerful Pokemon species that the Ultra Guardians have to figure out how to handle. It could be a Pokemon with unique abilities that pose a threat to the existing ecosystem in the Pokemon world.
One aspect of Pokemon Sun and Moon Ultra Guardians fanfiction could be the character development. The Ultra Guardians in the original game have unique personalities and abilities. In fanfiction, writers might expand on their backstories, like how they came to be part of the Ultra Guardians. For example, they could explore the early training days of a character and how they overcame difficulties to be a competent guardian.
In Pokemon Lake Guardians fanfiction, the three Lake Guardians, namely Uxie, Mesprit, and Azelf, are the central characters. They each possess unique powers. Uxie is known for its knowledge - related powers, Mesprit for its connection to emotions, and Azelf for its strong willpower. Other Pokemon or human characters might also be included depending on the plot, but these three are the main focus most of the time.
A common theme is the power of unity. The Ultra Guardians often work together in the original concept, and this is emphasized in fanfiction. They rely on each other's skills and Pokemon to overcome challenges. For instance, when facing a powerful Legendary Pokemon, they combine their efforts and strategies.
A delivery driver who drinks Monster Ultra to keep up with the fast - paced work. He might encounter all sorts of interesting characters during his deliveries and have some exciting adventures, so he could be a great main character. He could also have a backstory about why he took up this job and how Monster Ultra has become an essential part of his daily routine.
Given that it's a Naruto - based fanfic, Naruto Uzumaki might be one of the main characters. He could be the one who discovers the existence of the eternal guardians. Sasuke could also be involved, perhaps in a conflict or alliance with these guardians. And if the fanfic focuses on the shinobi world as a whole, characters like Kakashi or Tsunade might also play important roles. As for the eternal guardians themselves, they could be unique characters with their own personalities and powers.
The main characters could include the most powerful counter guardians who are tasked with protecting the universe from the alien menace. There could also be an alien character who has a change of heart and decides to side with the counter guardians, and their journey of self - discovery and integration into the counter guardians' world could be a major part of the story.
Since we don't have much information about this 'guardians novel', the main characters could be people with extraordinary powers who have been chosen or have volunteered to be guardians. They might come from different backgrounds, and their individual stories could contribute to the overall plot as they work together to fulfill their guardian duties.
I'm not entirely sure as it's a fanfic, but it might be about Pokémon in the Altomare region being guardians in some way. Maybe they protect the city, its people, or some important artifacts or secrets.