The village of Konoha would be in chaos. Naruto was seen as a hero, and if his dark side kills Sasuke, it would shatter the trust of many. His friends like Sakura would be devastated. She might go on a revenge quest against Dark Naruto. The Uchiha clan, which Sasuke was part of, would also be in turmoil. They might see this as an act of aggression against their clan and seek justice.
The village elders in the fanfiction might see it as a threat and immediately start planning to stop Dark Naruto. They would view his betrayal as a sign of instability and danger to the village's safety. This could lead to a divide in the village, with some believing Naruto can be redeemed and others thinking he should be eliminated.
At first, Jiraiya would be in shock. He couldn't believe that Naruto has become so dark and left him. Then, he would be determined to bring Naruto back. He would follow Naruto's trail, trying to understand his motives. Along the way, he might face some challenges from Dark Naruto's new allies or the places he visits. But Jiraiya would not give up easily, as he truly cares about Naruto and wants to save him from the darkness.
Well, in the 'Fall of the Dark Brotherhood Story', it might tell of how the Dark Brotherhood, which is usually a secretive and often feared assassin - like organization in many fictional universes. Their fall could be due to a hero or a group of heroes who decided to take them on. Maybe they were getting too powerful and attracting too much unwanted attention, so various factions united against them. It could also be because of a schism within their own ranks, where different ideologies clashed and tore the organization apart from the inside.
I'm not sure specifically as it depends on the particular version of the 'Fall of the Dark Brotherhood Story'. But it could include leaders within the Dark Brotherhood and those who oppose them.
However, Naruto also has a big heart. In the long run, he would probably try to find a way to save Kakashi or bring him back to the right side. He wouldn't give up on Kakashi easily, believing that there must be some underlying reason for his actions and that he can be redeemed.
He might initially try to prove his innocence. He'll gather evidence or find people who can vouch for him. But as the situation worsens, he could become angry and more determined to find out the truth and expose those who are behind his false accusation. He might even leave Konoha to seek answers and allies elsewhere.
He might be amazed. Naruto is used to his own world and seeing a fan - made interpretation like an AMV fanfiction would be like seeing a new side of his story.
Naruto would probably be angry at first. He's always been a free - spirited person, and being kidnapped by Sasuke, his friend - turned - rival, would surely make him mad. He'd likely try to fight back immediately, using his ninja skills and his never - give - up attitude.
At first, Naruto is likely to be heartbroken. Konoha has been his home, and he has always longed for acceptance from the villagers. So being abandoned would be a huge blow to him.