Sasuke would likely be conflicted. On one hand, he and Naruto have a deep bond, but on the other, Sasuke has his own ideas about justice. He might try to stop Naruto at first, reasoning with him. If that fails, he could be forced to choose a side, either to support Naruto's cause if he believes there's some merit to it, or oppose him to protect the shinobi world as he knows it.
Kakashi would be deeply troubled. He's seen Naruto grow up and has always believed in him. He would probably try to understand Naruto's reasons first. Kakashi would attempt to talk Naruto out of it, using his own experiences and their relationship as a teacher - student. If that didn't work, he'd have to face the difficult decision of whether to fight against Naruto, which would be a very painful choice for him.
The villagers of Konoha would be in shock. They've always seen Naruto as their hero, the one who saved them from Pain. But if he starts a war, they'd be divided. Some would still believe in Naruto and think he has a good reason, while others would feel betrayed. This would cause a lot of internal strife within the village, with different factions forming depending on their stance towards Naruto's actions.
In a fanfiction scenario where Naruto starts the 4th Shinobi War, it would completely change the whole Naruto universe's narrative. Naruto is known for his desire for peace, so if he starts the war, it might be due to some extreme manipulation or a misunderstanding of the situation. For example, he could be tricked by an enemy who has disguised themselves as an ally and convinced Naruto that starting the war is the only way to protect the Leaf Village. This would lead to a situation where all his friends and comrades would be forced to either oppose him or be dragged into a war they didn't want.
Well, one possibility could be that Naruto is somehow influenced by a dark force. Maybe he discovers some dark secrets about the shinobi world that make him believe war is the only way to bring about true change. He might start by attacking the Five Great Nations, thinking he can overthrow the existing power structures and create a new, more just world.
If Naruto was an Ajin in a fanfiction, the characters in Naruto would have a mix of reactions. Hinata would be concerned for Naruto's well - being. She might be a bit scared at first because of his new and strange abilities, but still stand by him. The villagers, who have had a rocky relationship with Naruto in the past, might be afraid of him all over again. They could see his Ajin powers as a threat. On the other hand, Naruto's close friends like Shikamaru would try to understand what's going on and help Naruto control his powers if they can.
Sakura would be extremely angry at first. She has known Naruto for a long time and would feel betrayed that he didn't trust her enough to tell the truth. But later, she would understand his reasons and might even help him if she could.
Naruto would probably be very curious. He'd want to know all about the bunnygirls, like where they come from and what their powers are. He might be a bit shocked at first, seeing as they're not like the people he's used to in the ninja world, but his adventurous spirit would quickly take over and he'd start making friends with them.
Sakura might be initially shocked and a bit scared of Robocop's robotic appearance. But once she realizes he's on their side, she would be interested in his technology and might even try to learn from it to improve her medical ninjutsu tools. Naruto, on the other hand, would be super excited. He'd probably want to immediately be friends with Robocop and would be eager to see what kind of cool moves he can do. Kakashi would be more cautious, observing Robocop carefully to assess his capabilities and motives.
They could have a range of reactions. Naruto would likely be excited and eager to see new stories about his world. He loves adventures and would be interested in seeing different takes on his life.
Some characters might be shocked. For example, Naruto himself would probably be really excited to see how his world is imagined in the future. He'd be happy to see that his story has inspired so many different ideas. Sasuke, on the other hand, might be a bit more skeptical. He'd analyze the fanfiction carefully, looking for any inaccuracies or misinterpretations of his character or the ninja world's values.
Naruto would be thrilled. He loves being the center of attention and seeing all these stories about him would make him feel even more important. He'd probably want to meet the writers and tell them how cool he thinks their ideas are.
Some might be amused. Naruto characters have their own set of stories and adventures, and seeing the different and often wild ideas in RWBY fanfiction could be a source of entertainment for them.