Well, Ruby might be shocked at first. She's used to seeing Jaune as a friend and teammate, so imagining him as Satan would be a huge contrast to her view of him. She might be a bit scared too, depending on how the fanfiction portrays it.
Yang would probably have a very vocal reaction. She's not one to hold back her thoughts. She might laugh it off at first, thinking it's just a wild and crazy idea. But if the fanfiction starts to get into some deep and dark themes related to Jaune being Satan, she could become more serious. For instance, if it shows Jaune causing harm to their friends in the story, Yang would be angry and protective.
If Jaune is betrayed, RWBY's relationships with him could become stronger. They might feel more protective of him. Ruby would be more attentive, Weiss might be less cold towards him, Blake could offer more support, and Yang would be like a big sister to him.
The RWBY team's reactions in the fanfiction when Jaune is betrayed would be complex. Ruby's reaction would be centered around hope and finding a solution. She'd likely try to talk to Jaune and see how he's feeling. Weiss would be outraged and demand justice for Jaune. Blake would be more introspective, perhaps relating the situation to her own past. Yang would be the most vocal and immediate in her anger. Their reactions would shape the further plot of the fanfiction, whether it leads to revenge, forgiveness, or something in between.
Well, Jaune in RWBY fanfiction can vary a lot. Sometimes he's the underdog who overcomes huge challenges, and other times he might have unique powers or a special backstory.
It could be because Jaune is a relatable character. He starts off as a bit of an underdog in RWBY. So, fans like to write stories where the other characters notice his potential and become obsessed with him as he grows.
One idea could be that Ruby and Jaune are partnered for a special mission outside of Beacon. Ruby's speed and combat skills combined with Jaune's strategic thinking could make them a great team. For example, they might be sent to investigate a mysterious Grimm activity in a far - off village. Ruby can quickly scout the area with her speed, while Jaune plans their approach based on the information she gathers.
One possible secret could be about his family heritage. Maybe in the fanfiction, Jaune has a hidden connection to a powerful family in the RWBY universe that he's kept under wraps for some reason, like to avoid unwanted attention or because of some family feud.