He'd probably be very intrigued. Percy has a penchant for adventure and new things, and this fanfiction would be something completely different from what he's used to.
I think young Sasuke would have a very intense reaction. He was so consumed by his hatred for Itachi at that young age. A Sasuke vs Itachi fanfiction would be like a trigger for him. He would be eager to see how the fictional fight is portrayed. If Sasuke in the fanfiction is shown as strong, it might fuel his own ego and make him strive even harder to become powerful. However, if the fanfiction shows Itachi as superior, it could enrage him. He might feel that it undermines his own goal of defeating Itachi and he might even want to find the writer to correct their 'wrong' view.
In fanfiction about Naruto and Demon Slayer with magic, one interesting aspect is the potential for new power - ups. For instance, a character could combine the Sharingan from Naruto with a Demon Slayer's special vision ability and create a super - powered form of sight. Also, the magic could be used to explain some of the more mysterious elements in both series. Maybe the curse marks in Naruto are actually a form of suppressed magic, and in the fanfiction, a character figures out how to fully utilize this magic, taking on a new and powerful form inspired by Demon Slayer's demon - slaying forms.
Magic in this type of fanfiction can be used to bridge the gap between the two universes. It can make the transition of characters from one world to another more believable. For example, if Naruto characters enter the Demon Slayer world, magic could be the reason they can adapt to the new rules and powers there.
I like Naruto in these fanfics because he always stays true to his beliefs. He is constantly trying to bring Sasuke back to the village and is willing to fight for their friendship.
One of the best moments is when they have a rematch that showcases their growth. Naruto has become stronger with his new jutsu, and Sasuke has further mastered his Sharingan powers. The intense battle of ideologies during the fight is captivating.
In this fanfiction, perhaps Sasuke could be a sort of anti - hero. He might initially be seen as a threat by the Demon Slayer corps because of his dark powers. But then, as the story progresses, he could use his Sharingan to detect demons more easily and work with the protagonists to defeat stronger demons.
Sasuke would be furious. He's always been protective of Naruto in his own way. He would immediately start looking for her, using all his skills and resources. He might even go on a rampage if he thought Naruto was in serious danger.
Naruto would probably be angry at first. He's always been a free - spirited person, and being kidnapped by Sasuke, his friend - turned - rival, would surely make him mad. He'd likely try to fight back immediately, using his ninja skills and his never - give - up attitude.
Naruto. His positive attitude and never - give - up spirit often inspire Sasuke. Also, his ability to connect with people gives them an advantage. He can rally support from unexpected places and his chakra is always a big boost in tough battles.