It's possible that new characters are introduced as main characters as well. They could be from a different village or have a special ability that ties into the 'different jutsu' aspect of the fanfiction. For instance, a character who has the ability to steal other people's jutsu and use them in unique ways, which would create a lot of conflict and interesting plotlines.
There could also be Sasuke. Since he and Naruto have a complex relationship in the original series, it would be interesting to see how it's developed further in this fanfiction. And Sakura might also be a main character, maybe with her medical ninjutsu taking on a new role.
One interesting concept could be new and unique jutsu that the characters develop. For example, a jutsu that combines elements in a way not seen in the original Naruto series.
Most likely Naruto would be one of the main characters, since it's in the title. There might also be his friends like Sasuke and Sakura as they are often involved in Naruto's storylines in fanfictions.
The 'Naruto Sexy no Justsu' fanfiction is important for the fandom because it promotes discussion. Fans can debate about the plausibility of the concepts in these fanfictions, like the mechanics of the jutsu or how it fits into the Naruto lore. It also helps to keep the Naruto fandom alive and active, especially during periods when there is no new official Naruto content. Fanfictions can fill that void and keep the fans excited about the Naruto world.
Well, Naruto is a given as a popular character in naruto different fanfiction. But Itachi also has a huge fan following in fanfiction. His complex backstory and moral dilemmas make him a fascinating subject for writers. Rock Lee is also quite popular. Fanfictions might explore his journey to become a stronger ninja in different ways, like giving him new techniques or different training regimens. And Sakura, despite some mixed feelings in the original series, has her own fanfiction following where her character is often rewritten or given more agency and growth.
Kakashi could be paired with Naruto as well. Kakashi, with his wealth of knowledge and experience, could guide Naruto in using his new and different powers. For instance, if Naruto obtains the power of space - time ninjutsu similar to Kakashi's Kamui, Kakashi could teach him how to use it effectively and avoid its potential drawbacks.
One popular 'Naruto Sexy no Justsu' fanfiction could be those that explore unique jutsu combinations in a creative way. For example, some might focus on how a new form of a jutsu could be used in a battle scenario that was not shown in the original Naruto series. It could also involve character development around the discovery and mastery of such a jutsu.
Percy is the main focus. There could be other demigods that are either intrigued or threatened by Percy's difference. Some might want to be his allies, while others might see him as a threat to the status quo at Camp Half - Blood. And his family, like his mother, would also play an important role in dealing with the changes in Percy.
There could also be characters in the new world who act as friends or foes to the main character. Maybe there's a wise old man in the new world who becomes a mentor - not in the Naruto - style but still gives useful advice. And of course, there might be antagonists who oppose the main character's rise with the Naruto system, perhaps fearing the change it brings.
Obviously Naruto himself. Then Sasuke would probably be involved as they have a deep connection. Sakura too, since she's part of their team. Kakashi might also play a role as Naruto's former teacher.
In a more futuristic world, a corrupt corporate leader could be the bad guy. He wants to use Naruto's abilities for his own profit, like making Naruto fight in illegal gladiator - like battles for entertainment. If Naruto refuses, he threatens to harm the people Naruto has grown to care about in this new world.