Sakura would be heartbroken. She would probably blame herself for not being able to protect Naruto. She might also start to train harder to fill the void left by Naruto.
The other genin competitors would have a variety of reactions. Some might laugh at Naruto, thinking he's being foolish. However, others might be inspired by his boldness. The proctors of the Chunin Exams could be either strict and try to stop him if it violates any rules, or they could be lenient and see it as a creative form of self - expression. And Naruto's friends from the village would likely cheer him on, seeing it as just another one of Naruto's unique antics.
She might be heartbroken. Hinata, being a shy and sensitive person, would likely retreat further into herself. She may feel that all her efforts to be brave and show her feelings to Naruto have been in vain.
One memorable moment could be when Hinata finally shows her true strength in a fight during the Chunin Exams in the fanfiction. Maybe she overcomes her shyness and uses a new jutsu to surprise everyone. For Naruto, it could be when he defends Hinata from some bullies during the exams. This shows his loyalty and growing feelings for her.
In fanfiction, the Chunin Exams often serve as a great backdrop for interactions between Gaara and Sakura. Gaara's complex character, with his troubled past, can have interesting dynamics with Sakura. She, being a strong - willed and intelligent kunoichi, might approach Gaara in different ways compared to in the original story. Maybe she tries to understand his pain during the exams, leading to a unique bond or rivalry that is different from what we see in the official Naruto storyline.
His friends would probably be very surprised. Shikamaru might be the first to raise an eyebrow, thinking Naruto is up to his usual unexpected antics. Sakura might be initially worried that Naruto is getting distracted from the real purpose of the Chunin exams. But as Naruto starts to play, they could end up being entertained and rooting for him.
Sasuke would likely be intrigued. He has his own dark path to some extent. He might see Dark Naruto's departure as a bold move and wonder if he could have the same courage. At the same time, he might also be a bit envious that Naruto is able to break free in such a way while he is still tied to the village in some ways.
Well, one thing that could happen is that Naruto, with his knowledge of future events, could easily ace the written part of the Chunin Exams. He might also be able to prevent some of the chaos that Orochimaru caused during the exams. For example, he could warn the proctors about Orochimaru's infiltration in advance.