It could be that there's a miscommunication between Naruto and the RWBY characters. Naruto's values and the way he does things are different from what the RWBY characters are used to. This difference in ideology might lead to the RWBY characters believing that Naruto is not on their side, and as a result, they betray him. His loyalty to his own village and ninja code might be seen as something negative in the RWBY world.
In this fanfiction, perhaps there's a power struggle. Naruto, being a powerful ninja, could be seen as a threat to the RWBY world's power balance. So, the RWBY characters, out of fear or a sense of self - preservation, betray him. They might think he'll disrupt their way of life or take over their territory.
If Naruto were betrayed in RWBY fanfiction, his values would be put to the test. Naruto believes in friendship and hard work. Being betrayed would make him question those beliefs. He might start to become more cynical, which would be a big change from his usual positive self. On the other hand, he could also use this as an opportunity to grow. He could learn about the different values in the RWBY world and try to find a new path. And perhaps, in the end, he would be able to forgive the person who betrayed him, but not without a long and difficult journey.
In this fanfiction, it might be that Sirzechs is being manipulated by some dark force. This dark force convinces Sirzechs that Naruto is evil. As a result, Sirzechs betrays Naruto. Naruto then has to not only deal with the betrayal but also figure out how to stop this dark force that is causing so much chaos and misunderstanding.
Perhaps in this fanfiction, Yugao is secretly working for a hidden organization that wants to get rid of Naruto. She betrays him by revealing his secrets or setting him up in dangerous situations. Naruto, being the kind - hearted person he is, initially doesn't want to believe she would do such a thing and tries to reason with her, but she is too far gone in her loyalty to the other side.
One possible plot could be that Jiraiya is forced to betray Naruto due to some external threat. Maybe an enemy has captured Jiraiya's loved ones and threatened to kill them if he doesn't turn on Naruto. Jiraiya, in a difficult position, might have to pretend to be against Naruto to protect his loved ones while secretly trying to find a way to free both Naruto and his family from the enemy's clutches.
Well, one possibility could be that Mavis has some sort of hidden agenda. Maybe she's being controlled by a greater evil force that makes her turn on Naruto. It could also be a misunderstanding. For example, false information is spread about Naruto, and Mavis believes it without proper investigation. Another idea is that Mavis has a different view of the ninja world compared to Naruto, and their conflicting ideologies lead to her betraying him.
Well, it could be that Kurenai is somehow deceived into believing Naruto has done something really bad. Maybe she's tricked by an enemy who fakes evidence against Naruto. So, in her misunderstanding, she turns against him.
In this fanfiction scenario, perhaps Mirajane has her own dark secrets or hidden motives that lead to her betraying Naruto. She might be seeking power and sees Naruto as an obstacle. Or, it could be related to loyalty to her own guild or group. If there are conflicting interests between Naruto's world and her world, she might choose to side against Naruto to protect her own people.
Well, it could be that they betray their village. Maybe they are tricked into believing false information about Konoha being corrupt. So they side with an enemy force, thinking they are doing the right thing.
Well, one possibility is that Naruto is framed for a serious crime he didn't commit. Maybe someone fakes evidence that he's been working with the enemies of the village. His friends, believing the false evidence, turn their backs on him. He then has to fight not only against the village's distrust but also to clear his name and find out who really set him up.
Perhaps Hiruzen is being influenced by some dark force or a hidden group within the village. They convince him that Naruto, with the Nine - Tails inside him, is too dangerous to be left unchecked. So, Hiruzen, in a moment of weakness, decides to betray Naruto. He could secretly arrange for Naruto to be sent on dangerous missions alone with the intention of getting him killed. Naruto, being oblivious to this at first, later realizes what's going on and has to fight not only against external enemies but also against the betrayal of his own village leader.