exactly!
Yess, also Roselia still knows from the novel that they are villains, she just wants to believe in them and that one day they'll change, and she just wants to help out Ein who's only a child, I mean it isn't obvious that a child would be a villain and act like one, so of course she'd rather not believe that, especially when he's so sweet, so yeah basically I agree hhh~!
I wouldn’t say ain is a villain at least not yet he’s been picking on them kids because they tried it with him first so as long as it doesn’t go too far I think his actions are within his right
The villains are actually villains in this story. They're manipulative, smart and deserving of the role given to them. I think a lot of us got disillusioned by all the isekai stories we've been reading, we forgot that it's difficult to change a person. You can't force change, the person themselves have to /want/ to change.
The mc being oblivious is intended. They never showed her anything that could lead her to believe that they're still evil. I'm certain the novel she read was sparse on the details. They are the antagonists after all. The information is usually kept on the minimum to create mystery around the character. It is no wonder separate movies are created explain the villain, they really give us close to nothing about their characters.