@Kate, I ttly agree with u about tht being the whole fun it speculating! It's such a good thing to discuss and speculate early on, so then we can look back and maybe even be able to speculate more until the ending. I really do love reading the different perspectives, it makes me think about what I haven't, and maybe I can grow in my thinking tht way.
Now, what u said about the person who tried to kill not being the same person who killed his family is one of the possibilities I was thinking of. Tht may very well be the case. I disagree about we never being able to find out who the killer is. I think we will.
I see what ur saying about how the father essentially IS the killer because he wrote it tht way. But I don't think of it tht way. I think the father did indeed write Kang Chul's family being murdered, but it wasn't malicious. It's not like he knew his work was going to come to life. He was just writing a story for all he knew, he was letting his creative juices flow. What I wanna know is WHEN did Kang Chul's world start to come to life. It could have been sometime before we saw Yeon Joo go into his world. Or, when the father got pulled into tht world, he could have been there for a really long time and thts when he made his decision to kill Kang Chul. But then again, Soo Bong said tht the father was planning on killing Kang Chul BEFORE he disappeared. So I think once we get a time frame for when Kang Chul's world first started to take shape, we'll be able to piece more things together.
I also don't think it multiple personalities. I don't think it's anything psychological at all. More alternate universes is a little far fetched, I know. Maybe it doesn't have to be more than 1 alternate universe, all I'm saying is tht I think it's some version of Kang Chul. Something tht the father created, so I guess if tht is the case, he didn't have to come from another alternate universe. But the more and more I think of it, I think there's another version of Kang Chul.