Itachi would probably be very calm and composed. He might see Sarada as a symbol of the new generation of ninjas in the village. He could be gentle with her, perhaps sensing her potential and her desire to grow as a ninja.
Sakura would be heartbroken. She'd likely spend hours upon hours by Naruto's side, trying to jog his memory with stories of their adventures together. She might even get a bit overbearing in her attempts. Sasuke, who has his own complex relationship with Naruto, would be conflicted. He'd see Naruto's forgetfulness as a sign of weakness at first but then realize the importance of their bond. Kakashi, being the experienced leader, would start by observing Naruto carefully to see exactly how much he has forgotten and then start a systematic process of helping him remember.
Their team dynamic would be quite complex. Naruto is very open - minded and friendly, always eager to make friends. Itachi, having been through so much in his life, is more reserved. Naruto would be excited to have such a powerful teammate like Itachi and would constantly pester him for tips on becoming stronger. Itachi might initially be annoyed by Naruto's boisterousness but would gradually come to respect his determination. In battles, Naruto could use his large chakra reserves and shadow clones to create distractions while Itachi uses his Sharingan to find the enemy's weak points and strike. They could form a formidable team if they could get past their initial differences.
One possible fanfiction could be about Sakura joining an Anbu team that has Itachi and Shisui. Maybe Sakura is a new recruit and she has to learn from the two experienced shinobi. Itachi could be the calm and collected leader, while Shisui is the more easy - going one who helps Sakura adjust to the harsh Anbu lifestyle.
Sakura would probably be initially terrified. She would try to use her medical ninjutsu skills to defend herself or at least slow Itachi down. If she realizes she can't overpower him physically, she might try to talk to him, asking him why he's doing this.
Sasuke would likely be devastated. Despite their past differences, Naruto was his rival and in a way, his closest friend. He might go into a deep state of regret and isolation. Sakura would be heart - broken. She loved Naruto, and his death would be a huge blow to her. She might become more withdrawn and focus all her energy on her medical ninjutsu. Kakashi would be filled with a sense of failure. He was Naruto's teacher, and he would feel responsible for not being able to protect him.
Sasuke might initially be indifferent on the surface, but deep down he would feel a sense of loss. He has always had a rivalry with Naruto, and Naruto's departure would mean an end to that dynamic. Sakura would be devastated. She has grown to care about Naruto as a friend and teammate, and his leaving would leave a big hole in the team.
Their relationship would start off a bit rocky, considering Itachi's past actions. But as they work together, Naruto would start to understand Itachi's motives more. Itachi, in turn, would see Naruto's growth and potential. Eventually, they would develop a mutual respect for each other.
One possible plot could be that they are tasked with protecting a powerful and ancient ninja artifact. Naruto's raw power, Itachi's strategic mind, and Yugao's stealth skills are all needed. Along the way, they face off against other ninja clans who also want the artifact for their own purposes. They have to battle not only the external enemies but also their own internal doubts and differences to succeed.
Sasuke could also be confused. He has always had a mix of emotions towards Itachi, including love, hate, and envy. Being kidnapped by him would add another layer of confusion. He might wonder if Itachi has some new plan or if he's finally going to reveal some long - hidden truth. So, he might hold back on his full - fledged resistance and wait to see what Itachi has to say.