Hmm, in a real situation, I would think Laura or the yandere will tell the MC her feelings about him, also Nicole will be saying things too, but in spanish so the MC can´t understand it. But ingame, just the yandere could make this just because of her need to possess you. For the rest of the girls, you´ll have to take that step.
Oh, and don´t worry about being a thick skull😅, the girls will change the way they treat you depending on your relationship with them. For example, Nicole now might be emotionless, but later she´ll be warm, or the bully starting rude and aggressive, and gradually becoming a bit more caring.