Jiraiya's reaction might be complex. He might be in awe of Naruto's new power but also sad about his departure. He could see it as a natural progression in Naruto's journey, yet still feel a pang of loneliness. He might start to reflect on his own life and training methods, wondering if he could have done something differently to keep Naruto with him. At the same time, he would be eager to see what Naruto will achieve in the world with his newfound abilities.
The Akatsuki members themselves would have mixed reactions. Some, like Itachi (if he were still alive in the fanfic), might see Naruto as a potential asset but also a threat to their long - term goals. Kisame might be amused by Naruto's presence and see him as a new source of entertainment. Meanwhile, the Leaf Village elders would be outraged. They would see Naruto as a traitor and start devising plans to either bring him back or eliminate him.
Naruto would be determined to get to the bottom of it. He would not just accept the betrayal at face value. He would use his skills and the help of his friends to investigate what made Jiraiya turn against him. Naruto's ninja way is about never giving up, and this situation would be no different. He would fight against this betrayal, both physically if Jiraiya became an enemy in combat, and emotionally, trying to understand the reasons behind it all while still holding on to the hope that Jiraiya could be redeemed.
Sakura might be very cautious at first. She's heard about the Akatsuki's bad reputation, so she would keep her distance. For example, if she sees an Akatsuki member lurking around school, she'd probably try to avoid them and alert the proper authorities, like the school security or her ninja mentors if it's in a Naruto - like world with ninja training in high school.
Some members like Itachi might be very calm and just observe quietly. He would probably analyze the stories, thinking about how the characters are developed and what the underlying themes are.
Naruto would probably be initially cautious but also curious. He has a knack for seeing the good in people, so he might try to befriend the Akatsuki sister. Kurenai, on the other hand, would be more guarded. She is a more experienced ninja and would be wary of any Akatsuki member. But she also might see an opportunity to gain intel from the sister.
He would probably also feel angry. After all, he has sacrificed so much for the village and for them. He might start to question his own beliefs and values. But Naruto being Naruto, he would not give up easily. He would try to prove his innocence and show them that they are wrong. He could go on a journey to find evidence or seek help from other allies who still believe in him, like Shikamaru or Kakashi.
Naruto might be initially very disappointed. He has always looked up to Jiraiya and expected to be trained by him. So, when faced with the refusal, he could be heartbroken and feel like he has lost a great opportunity.
The other members of the Akatsuki would have mixed reactions. Some, like Itachi (if he were still alive in this fanfiction), might see Naruto as a glimmer of hope for the group to change its ways. He could work with Naruto to steer the Akatsuki towards a more positive path. But others, who are more set in their old ways, might resist Naruto's presence and try to undermine him. The villagers of the Leaf would be shocked and confused. They've always seen the Akatsuki as the enemy, and Naruto joining them would be a huge paradigm shift for them.
The Naruto fandom would likely be very divided. Some fans would be extremely outraged as it goes against the core values and character of Naruto. They might condemn such a fanfiction.