my final judgment on this ： it was a failure
yes it was a gripping drama to watch but 、went completely off the rails with episode 11 totally over romanticised shading into melodrama and episode 12 just bad melodrama with I assume the triumph of evil embodied in Kim Changjun and the principal and of social advantage ー
but then there are the unresolved questions starting with the end of episode 11 and Kim Hwan on the edge.......of what? a watery grave. ? bizarrely we do not find out specifically in episode 12 where the one actually taking the plunge is Jeon though the very end maybe can be viewed as implying he joins the other ghosts （but no not all of them actually died or at least bodily）
I am still not clear if Cein's mother was responsible for her own fate or raped and murdered by Kim Changjun though given his later easy turn to murder to attain his ends and hints from the principal' s contributions in the drama including the flashback to the young Changjun I tend to the latter view but the writer really leaves it hopelessly muddled
you can take this as an invitation for your imagination to fill in the gaps or a failure of the writer to properly resolve the drama： I am quite willing to let my imagination run but if so it will not be because the writer [webtoon or screenwriter] encouraged me to do so in a positive way but because I have to make up for their inadequacy