It's a weird dynamic. Park Yungrok obviously is being painted in a somewhat sympathetic light with his sister, yet he's set up as the explicit antagonist for the moment. On the other hand, Cha Yuri is a very clear antagonist who was a massive asshole against the MC (she is the reason the teacher beat him), yet here's she's basically on his side.
I really hope it does not go the super bullshit trash route that too many series go down, where the female characters get absolutely no punishment for their behavior yet the male characters get beaten up for the same or not as bad actions. I guess I'll have to wait and see.