Well, if Hidan mistakes an OC (original character) as a Jashin fan, there could be some wild consequences. He might try to involve the OC in his Jashin - related rituals. Since Hidan is extremely devoted to Jashin, he could see this as an opportunity to either convert the OC or use them as a sacrifice. It would be a really chaotic situation for the OC as Hidan is not one to be reasoned with easily when it comes to his beliefs.
The consequences might be that Hidan would start to test the OC's loyalty to Jashin. He could put the OC through various dangerous and extreme trials. For example, he might make the OC fight against his enemies, believing that if the OC is a true Jashin follower, Jashin will protect them. If the OC fails, Hidan might consider them a false follower and punish them severely.
If Hidan mistakes an OC as a Jashin fan in a fanfiction, it could lead to the OC being dragged into Hidan's world of blood and sacrifice. Hidan may assume that the OC has the same views on death and pain as he does. He would likely force the OC to participate in his cruel and violent practices. This would completely disrupt the OC's life or story within the fanfiction, and they would have to either find a way to escape Hidan's clutches or somehow convince him that they are not what he thinks.
The OC could try to explain to Hidan that they are not a Jashin fan. They should be very clear and firm in their statement. For example, they could say something like 'I have no relation to Jashin, you are mistaken.'
Mistakes in the OC's powers or abilities can also be an issue. For example, if the OC has a power that seems too overpowered or not powerful enough compared to what's expected in the Jashin - themed story. You can hide this by introducing the concept of Jashin's fickleness. Say that Jashin sometimes bestows great power randomly or takes it away, and that's why the OC's power level fluctuates. This way, it doesn't seem like a mistake in the OC's design but rather a part of the Jashin - influenced world.
One way could be through careful editing of the plot. If there are mistakes in the OC's backstory, for example, you can subtly rewrite parts of the story so that it seems like the actions or characteristics that were mistakes are actually part of a more complex, hidden plan related to the Jashin faith. Maybe the OC has some seemingly inconsistent behaviors, but you can explain them as being influenced by Jashin's teachings in a very unique way that makes the mistakes seem intentional.
In a 'jashin x hidan fanfic', the author may take creative liberties to develop their own storylines. For example, they could create a scenario where Jashin gives Hidan special powers or tasks. It could also delve into Hidan's loyalty to Jashin and how that affects his actions and decisions in the fic.
The OC could be an outcast in the ninja world. They don't belong to any major clan and are constantly on the move. Hidan might see this OC as an easy target. The OC might have some unique skills, like being able to communicate with animals, but these skills are not enough to protect them from Hidan when he decides to sacrifice them for his own dark purposes.
In a 'Hidan Sacrifices OC' fanfiction, the OC could be a sacrifice to stop some greater evil. Hidan, believing in his twisted way that sacrifice is the answer, chooses the OC. The OC might be an innocent bystander or someone who was in the wrong place at the wrong time. However, the sacrifice could have unforeseen consequences. Maybe it angers other characters in the Naruto universe who then seek revenge on Hidan for his cruel act.
Well, it could be about an original character who gets caught up in Hidan's sacrificial rituals. Maybe the OC is a new recruit in the Akatsuki and Hidan decides to use them for his Jashin worship. The OC might have some special power or knowledge that either makes them a prime sacrifice or a target for Hidan's wrath.
Another theme could be power. Since Jashin might be seen as a source of power for Hidan, the fanfic could focus on how Hidan gains or uses this power in different situations, and how it affects his relationships with others.
One idea could be that your OC is a new recruit to the Jashin cult. They start off being naive about the true nature of Jashin's teachings but gradually discover the dark and extreme aspects as they get more involved. For example, they could be sent on a mission to sacrifice a powerful being to prove their loyalty.
The Akatsuki would surely be affected. They would lose one of their members, which could disrupt their plans. Also, it might change the way other characters view Naruto. Some might see him as a more formidable threat, while others might see him as a hero for taking out a dangerous enemy.