I'm not quite sure what the teacher's motive here is yet. Perhaps she thinks her Hoshino brought out something special in his art? Or she'd just prefer if the two people she likes at this school got to know each other better so they weren't on bad enough terms to end up with one of them being the object of a hate-portrait by the other.
Let's just read again, after 4 years of dropping half way because I know the ending, I don't remember shit. I do remember this manga started out good tho