A possible plot could involve Naruto's friends being influenced by a dark power. This power convinces them that Naruto is a threat to the village. They then betray Naruto by trying to assassinate him. Naruto, being the kind - hearted person he is, is initially confused and heartbroken. He has to then decide whether to fight back against his friends or try to find a way to break the influence of the dark power on them.
One possible plot could be that Naruto discovers his friends have been secretly working with an enemy. They might have been promised power or something valuable in return for betraying Naruto. Maybe they spread false rumors about Naruto, turning the village against him.
It could be that the whole Team 7 is brainwashed by an evil ninja with powerful genjutsu abilities. They are made to believe that Naruto is the key to a great evil that will destroy the ninja world. As a result, they turn on Naruto, and he has to fight not only his former teammates but also the false accusations and the real threat behind the brainwashing.
One possible plot could be that Konoha's leaders, fearing Naruto's growing power, secretly plan to get rid of him. They spread false rumors about him, turning some of the villagers against him. Another plot might be that they frame Naruto for a crime he didn't commit, perhaps a major attack on the village, in order to justify exiling or imprisoning him. A third possibility is that they withhold important information from Naruto that could put his life in danger, all in the name of protecting the village's secrets.
In some fanfictions, it could be that Harry discovers a dark secret about the wizarding world that his friends don't believe or are too afraid to accept. His friends, thinking he has gone mad, side with the established order. They then betray Harry by reporting his so - called 'crazy ideas' to the Ministry of Magic, leading to Harry being hunted.
Naruto would likely become more distrustful at first. He's always been so open and trusting of his friends, so this betrayal would shatter that. He might become more withdrawn, constantly second - guessing people's motives.
Perhaps in the fanfiction, Natsu is betrayed by someone he trusts in a mission. For example, they might leave him behind in a dangerous situation to fend for himself while they take the credit for the mission. Or it could be that a love interest betrays Natsu by choosing someone else over him due to some false perception or external pressure.
One common theme could be Ash's feelings of isolation and despair. After being betrayed, he would likely feel very alone and question his past relationships.
Maybe Natasha, in this fanfic, could be working undercover among Naruto's group for some secret mission. She gains Naruto's trust over time, but then reveals her true motives which are against Naruto's goals, thus betraying him.
A plot could revolve around the power vacuum left by Naruto. The Leaf Village is in disarray, and other villages start to make moves against it. Pain might realize that killing Naruto wasn't really what he wanted in the long run, as it led to more instability. Or maybe a character who was in the background in the original story steps up to try and fill Naruto's shoes. They struggle to gain the respect and power that Naruto had, while also dealing with the grief of his loss.
I'm not sure of specific fanfics on this topic offhand. You could try searching on popular fanfic platforms like Archive of Our Own. Just type in the keywords 'ash gets betrayed by most of his friends' in the search bar and browse through the results.
At first, Naruto would be in disbelief. He has always trusted his friends wholeheartedly, so this would be a huge blow. He might then feel a deep sense of anger and sadness. However, Naruto being Naruto, he would likely also start to look for ways to prove his innocence or the misunderstanding. He might go on a journey of self - discovery to figure out what went wrong and how he can win back his friends' trust, all while dealing with the pain of the betrayal.