Hii, since they have been giving hints on who is the murderer here, i would say its only seongbin and yes only him, yujeong and the guy who attempted suicide isnt...why? Cause they're mentally unstable too a guy who is short and fragile, who also have schizophrenic thingy cant be the murderer in this cases. since they said that hyeeseong was excited or happy before she died, And before she died it was confirmed on this chapter that its seongbin who she seem to have a feelings with. I like to say that seongbin just killed her because of water thingy, but no, water isn't enough for them, i think its because they are exhausted and needed some energy soooo they found something that can answer their cravingness, they also ask what they're blood type is, they discover each other who is compatible of who, seongbin killed her just to drink her blood or other organs so he could get an energy?, (they also killed yun but i think her blood is not compatible to him thats why he just let it slide(i also think he kill her (yun) to reduce the consument of the water) (please dont believe any of thins this is just me saying my delulu thoughts hehe)
Don't judge a book by its cover, but you're not a book so i can judge you
