There would likely be a sense of determination as well. Reading about the fight could strengthen his resolve to actually face Itachi in real life and prove his strength.
He might feel anger. Since he was so set on revenge against Itachi, any portrayal that didn't match his view of himself as the victor could make him angry.
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.
Staying true to the Naruto universe's lore can be a challenge. There are many established facts about their relationship and abilities. If you deviate too much, it can feel out of place. For example, if you give Sasuke a power that doesn't fit with the chakra system in Naruto, it might seem off.
Sasuke would likely become more protective. Usually Sasuke is very focused on revenge and his own power, but when faced with baby Itachi, he would feel the need to shield him from all harm. His cold exterior might soften a bit as he looks at the innocence of baby Itachi.
Most likely Naruto and Sasuke. In the original series, they were already very powerful when they faced Kaguya, and in fanfiction, they could be even more so. Their combined strength and determination usually make them the favorites to win.
One interesting plot could be a story where young Sasuke dreams of surpassing Itachi not just in combat skills but also in understanding the true meaning of protecting the village. It could show their early training days with Itachi trying to teach Sasuke important life lessons in a more brotherly way.
First, make sure you're familiar with the Naruto and Sasuke relationship in the original manga or anime. This will help you better understand and appreciate the fanfiction. Second, don't be afraid to try different genres within the Naruto vs Sasuke fanfiction. It could be action - packed, angsty, or even have a touch of romance. Third, pay attention to the writing style. A clear and engaging writing style can make a huge difference in your reading experience.
He could be feeling a sense of calm. Naruto has a certain presence that even in sleep can be soothing. Sasuke, who has had a tumultuous life, might find peace in just observing Naruto at rest.
One great 'Sasuke and Itachi Fanfiction' is 'The Bond Beyond Blood'. It delves deep into their complex relationship, exploring the unspoken emotions between them. The story is set in an alternate universe where they have to team up against a new, powerful enemy. It shows how they gradually come to understand each other better in the face of danger.
In this kind of fanfiction, Itachi might use his powerful Sharingan abilities. He could perhaps create illusions to mislead Orochimaru and his minions, then quickly snatch Sasuke away. For example, he could make Orochimaru think that Sasuke is in a completely different location while he secretly approaches and rescues him.
In many fanfictions, Sasuke starts as a character full of anger and a thirst for revenge. But in the context of a relationship with Itachi, he begins to soften. He starts to see Itachi in a different light, beyond just the person who killed their clan. Itachi, on the other hand, is often portrayed as a complex figure with many secrets. In these fanfictions, his love for Sasuke makes him more vulnerable and human. For example, in some stories, he reveals his true motives to Sasuke, which changes their dynamic.