
Spoilers:
Who? Dohui was hurt by the ghost he had a connection and deal with. The ghost fell in love with Seong and Dohui was in a relationship with him so he was mad. Also because of the deal with the big guy in blue
The big guy in blue. I think he felt the pain the ghost felt when Seong held the stick because he made a pact with him. He wanted Dohui to die because he thought he was the reason his (half?) brother died.
Seong is alive but hurt
The small brother guy is dead.

So, the big guy in blue I mentioned is the “sir” in chapter 25 and the small guy I mentioned is Sooyeon. Sooyeon is I think the half brother of sir. I think Seong is a nephew of sir so he got to stay there with Dohui for an exam they all had to take. Sir is in love with Sooyeon and he r*pes him once so sooyeon wants to kill him. Sooyeon is also illegitimate so he is not accepted by the family. All four of them were together in the same place for most of the story.
Sooyeon fell in love with Dohui. Sir is mad at Dohui and seong has a relationship with Dohui
Sooyeon and Seong are friends. Sir and Seong are cousins I think?
Sooyeon and sir are some sort of brothers.
I hope this explains it
Can some one plz explain whats Happening? Im confused? And how did the other Person die ?