The Akatsuki members might see Gojira as an opportunity. They could try to capture it or use its power for their own evil purposes. Itachi, if he were still around, might try to stop them from doing something stupid that could lead to even more destruction. Naruto would have to not only deal with Gojira but also fend off the Akatsuki's attempts to use the situation to their advantage.
Sakura would probably be terrified at first. She might initially think it's a new kind of giant summon gone wrong. But then she would gather her courage and try to help Naruto deal with the situation, maybe using her medical skills to heal any injured people in the chaos. Kakashi, on the other hand, would be very calm and start observing Gojira's behavior to figure out a strategy.
One possibility is that the reverse summoning is part of a secret jutsu gone wrong. Gojira's arrival might disrupt the balance of chakra in the Naruto world. The plot could involve Naruto seeking out ancient scrolls or wise sages to understand how to deal with this unexpected situation. He might also have to team up with his friends, like Sasuke, to control Gojira's power and prevent it from destroying everything.
The older generation, like Kakashi, would be very cautious. He has seen a lot in his life and would be worried about the implications of Naruto having such god - like powers. He would try to guide Naruto to use these powers responsibly, fearing that Naruto's inexperience with such power could lead to chaos in the ninja world.
Harry could be both curious and cautious. Curious because it's an entirely new situation and he might be eager to learn about this strange new group. Cautious because he doesn't know their intentions. He has been through a lot in his life and has learned to be careful. He would likely approach the situation with his wand at the ready, just in case. And he would be constantly observing their actions and trying to figure out what they want from him.
Naruto would likely be excited yet a bit scared. He'd be eager to make the future a better place but also worried about the bad things he might see. Sasuke would probably be more reserved, analyzing the future information carefully. Hinata would be shy about it but also determined to protect those she loves if she saw any danger in the future for them.
Naruto would react with his usual enthusiasm. He'd see the succubus as someone he could potentially help or befriend. He might not fully understand what a succubus is at first, but his kind nature would lead him to approach her without fear. As for Kakashi, he'd be more guarded. He'd analyze the situation carefully before making any moves, while also keeping an eye on Naruto to make sure he doesn't get into too much trouble.
Sasuke would likely be very suspicious at first. He has always been on guard around Naruto, and this new revelation would make him even more cautious. He might see Naruto as a potential threat to the village or to his own goals.
Iruka would probably be one of the first to notice and try to step in. He has always been like a father figure to Naruto. He would likely confront Kushina and try to protect Naruto. Sasuke might be a bit more conflicted at first. He has his own issues, but seeing Naruto being abused, he would probably end up on Naruto's side and try to figure out what's wrong with Kushina.
Sasuke would be deeply affected. He and Naruto had a complex relationship. His first reaction might be shock and then a deep sense of loss. He might feel guilty for not being there to help Naruto. Sakura would be heartbroken. She had always cared for Naruto, and his death would be a huge blow. She might become more determined to protect the village in his memory. And Boruto, Naruto's son, would be devastated. He would probably grow up with a strong sense of purpose to live up to his father's sacrifice and protect the village even better.
Sakura might be initially shocked and then start laughing uncontrollably. She would probably tease Naruto about it for a while. Sasuke, on the other hand, would likely just give a slightly raised eyebrow and then act as if it's not a big deal, but deep down he might be a bit amused. Kakashi would probably make a dry joke about it.
He might be surprised. Fanfics can be full of wild ideas that he never thought of, like strange pairings or new jutsu concepts.