Sakura would be greatly affected. If the new Naruto is different, she might have a hard time adjusting. She was used to the old Naruto's clumsy but sincere attempts at flirting and his unwavering loyalty. A new Naruto could make her question her feelings and role in the group.
Kakashi would also notice the change immediately. He'd be on high alert as he tries to figure out what's going on. He might be more strict with this new Naruto, especially if he senses something off about him. His teaching methods could change to better understand and train this new version.
In this type of fanfiction, the plot might develop in a way that Naruto tries to fix things he previously thought were okay. For instance, he could decide to reform the ninja academy's training system. He has the experience of being a student there, so he knows the flaws. This would then lead to him facing opposition from the traditionalists in the village, creating a lot of conflict and drama in the story.
One possible plot twist could be that the new Naruto has different abilities. Maybe he has a unique form of chakra control that the original Naruto didn't have. This could lead to different battle strategies and interactions with other characters. For example, in a fight against Sasuke, he might use his new chakra control to create unexpected jutsus.
The storyline would change a lot. For starters, Naruto doesn't have the Sharingan like Itachi. So, all the battles and strategies that relied on Itachi's Sharingan abilities would be different. Naruto would have to rely on his own skills, like the Rasengan and his Sage Mode. Also, Naruto's interactions with the other characters in Itachi's world would be different. People in the Akatsuki might not trust him as easily as they did Itachi, or they might be more curious about him because he's so different.
The story would change drastically. Naruto's presence in Itachi's role would mean a different set of values driving the actions. Naruto values friendship and believes in the good in people. So, in dealing with the Akatsuki, he might try to convert some of them rather than just eliminate them.
For Kakashi, it would be like losing his student all over again. He has trained Naruto and seen his growth. His death would make Kakashi question his own role as a teacher and mentor. He might become more withdrawn and blame himself for not being able to prevent Naruto's suicide.
Sasuke might be affected as Naruto's closest friend. With Kushina back, Naruto could be more at peace, which might change the dynamic of their relationship. Sasuke could see a different side of Naruto, one that is more complete with his mother's presence.
Well, one possibility is that the 'new' Naruto, who is actually the original Naruto in a different role, could change the course of events in the Hidden Leaf Village. Maybe he would approach missions and training in a completely new way, leading to different power-ups and relationships with his comrades.
The other ninja villages would view Naruto very differently. They might see him as an even greater threat now. This could lead to more tense relations between Konoha and the other villages. At the same time, some younger ninja from other villages might idolize Naruto even more and try to learn from him, hoping to gain some of his power. This would create a complex web of relationships and power dynamics in the Naruto fanfiction world.
Sakura would be deeply affected. She has been Naruto's friend and teammate for a long time. His departure would make her feel guilty, thinking that she could have done something to prevent it. She might also worry about his safety out there alone.
If he reveals a powerful secret, it could change the power balance. Other villages might see him as an even greater threat or an ally they must court. For example, if he reveals a super - strong jutsu, enemies might be more hesitant to attack Konoha.