I have no doubts that it's Jean. How much the other two are involved I'm not sure, but Jean has too much evidence against him for him to not be involved.
Some people are saying they are working together, but the conversation they have in private indicates that they don't know why Eda is acting that way or are trying to hide it from the others. Which you wouldn't do if all three were in on it and talking in private. If they are doing it then they are doing so individually without the other two knowing.
I don't think the Prince is involved at all.
What you wrote, makes sense... hopefully the author goes with something that would make sense.
I just want to know who's the evil man? I'm not that good at guessing. They all look suspicious and horny for MC.