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.
Naruto could be one of his allies. Naruto has this knack for seeing the good in people and would probably be willing to give Obito a chance to redeem himself. Also, Sakura, with her skills as a medic - ninja, could be an ally. She might help heal Obito if he was injured during the war and see the potential in him to be a force for good.
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.
The fanfiction could explore how Obito's identity revelation affects his relationship with the Akatsuki. Some members may feel used or deceived, while others might see it as an opportunity. It could also show how Obito's true self starts to form new bonds or break old ones within the organization, depending on how his true intentions are perceived.
One possible motive could be to use Sakura as a bargaining chip. If he has some sort of plan against Naruto or the Hidden Leaf Village, Sakura, being a close comrade of Naruto, could be very useful. He might think that by restraining her, he can force Naruto to come to a certain location or make concessions.
One popular sakura and obito fanfiction is 'The Unseen Bond'. It delves into a world where Sakura discovers Obito's hidden past and tries to help him find redemption. Another great one could be 'Sakura's Encounter with Obito', which focuses on their chance meetings and how it gradually changes their relationship. And there's also 'A New Path for Sakura and Obito' that shows them working together to face challenges in the ninja world.
The sad story of Obito and Rin is a key part of the Naruto narrative. Obito was a young ninja with big dreams and a huge crush on Rin. When Rin was seemingly killed in front of him, it shattered his world. He thought that the ninja world was full of pain and betrayal. This led him to be influenced by Madara. He became one of the main antagonists, all because of his love for Rin and the unbearable pain of losing her. His journey from a hopeful young ninja to a vengeful villain is a tragic consequence of Rin's death.
Well, it could be about Sakura somehow being related to Obito in a reincarnation context. Maybe it involves Sakura having memories or powers that are linked to Obito from a past life. It might explore how this new connection changes their relationship in the Naruto universe, like if Sakura starts to understand Obito's past actions better or if she gains new abilities because of this reincarnation bond.
In fanfiction, Naruto sacrificing himself for Obito could be a very emotional and dramatic concept. It might show Naruto's ultimate selflessness, believing that Obito is worth saving at the cost of his own life. This could be due to Naruto seeing the good in Obito that others might not, like the part of Obito that was once a kind - hearted shinobi.