LOL! I'm not a BL fan but the chemistry between Ji Sung and Park Jin Young is absolutely freaking insane. I'm definitely a shipper when they are onscreen.
I've never seen JI Sung play a dark character but his acting and this screenplay are so good that I can't guess whether he is the devil, a saint in devil's disguise or just someone who amuses himself at the expense of others. Because the drama has an intensity of 10+, I have to take it in small doses because my emotions get too wrapped up in the scenes. As far as guessing what's going to occur, I think eventually the student outwits the teachers and Kim Ga On will become the top judge.