Okay, this may contain some spoilers ..

1st, maybe I missed it somewhere, but can anyone tell me, WHO IS THE GIRL that was with little Ba Reum, who stepped on and crushing a mouse to death just like that and I think that's the 1st thing that aroused Ba Reum's killer instinct ?
Anyone remember the girl ? She was older than Ba Reum .. or maybe that's just not that important to be detailed later on, like from whom Wu Yeong Cheol (did I spell it right) the psychopath killer that also almost killed Ba Reum, got his psychopath gene ? Coz his father was a (good) cop and his mother also seems normal, though maybe she really ever had an affair as WYC said

2nd, if Ba Reum really was adopted (and switched with Yo Han) by another woman, when did it happen ? I mean at what age and why the woman willing to adopt Ba Reum, if she knew from the start that Ba Reum is the Head Hunter' son ? and what is expected to happen by Ba Reum's mother and the adoptive mother to switch their son ???

3rd, okay maybe it's just to add dramatic, tragic, heartbreaking point by not doing it, but if I was Moo Chi's brother, once I got the chance to speak to Moo Chi by phone, though my neck was stuck on a knife, I'll certainly yell to my brother who is actually the killer, hahahaa ..

And I can't even understand why that PD Choi chose not to return to her family just because she felt "guilty" for being an "accomplice" of the Head Hunter .. She was just a kid and certainly was forced, who would blame her ? She was "torturing" her parents, especially her mother by doing so actually ..

It's even weirder when the OZ came out .. I thought it would be better if it's just a story about a psychopath, not a "Customized" psychopath ..

Well, I don't think I'm enjoying it .. sorry, for those who think this is a masterpiece or anything like that .. so many loopholes ..