I don't think it's Dad cause the drama does have subtle healing theme and that seems too dark. I do kind of think…
I don't think the killer needs 35 years to find Haejoon. Haejoon was an anchor on TV, so the killer should have known a lot earlier. Also, he's the principal grandson. At some point, when he's 20-25, the killer might have recognized him.
I don't know if this drama is going to be that dark, but my theory is that ML's dad is the killer. This drama started with the FL trying to separate her parents, but it's actually the ML who will do that to save his mother (who can be a victim), thus erasing his existence. This also ties with the FL's dream and the ML does turn out to be the perfect stranger -- he came out of nowhere, saved her family, and vanished.
Everyone missed an important question: why was ML killed in 2022 when he wasn't even part of that village during the murders? There's no reason for him to meet the murderer. He might have found have some evidence that his dad killed his mother. After that, ML might have died accidentally after going through a struggle with his dad in 2022. The dad then creates the time machine and ensures that the ML can found it and save himself, which means stopping the dad in the past. The only problem with this theory is that ML's dad was supposed to be in the US, but if he's really a killer, then he might have lied about it. Other than ML's dad, I think only a new character can be the killer.
I read a theory on Reddit that future Mi Sook is the killer. She timetravels to killer her victims. It does make sense considering how Mi Sook thinks the killer can't be caught.
bcos people thought that she ran away.Her dead body was never found so,no one got to know that she is a victim.
But, the missing girl who the ML saved earlier, also went missing after leaving a note. If she was considered missing, then why wasn't ML's mom considering missing, even if she left a note?
ML's mom definitely seems like a victim or at least she didn't abandon him. But, if she was a victim, why is there no record of her case in the future?
I think Mi Sook only blamed her brother for the murders to make him a worse child in the eyes of her mother. This begs the question: how does she know about the details from the murder? If it someone that scares Mi Sook, then it can only be her father. Her mother doesn't seem like a murderer.
Everyone missed an important question: why was ML killed in 2022 when he wasn't even part of that village during the murders? There's no reason for him to meet the murderer. He might have found have some evidence that his dad killed his mother. After that, ML might have died accidentally after going through a struggle with his dad in 2022. The dad then creates the time machine and ensures that the ML can found it and save himself, which means stopping the dad in the past. The only problem with this theory is that ML's dad was supposed to be in the US, but if he's really a killer, then he might have lied about it. Other than ML's dad, I think only a new character can be the killer.