@Martin I'm quite aware. Yet, since I don't believe the man in black is a character, I don't agree his father's behind that one but you're right at one point: his family's killer (the one I wrongly named to be the real one) is (or most definitely SHOULD be) a character. Then again, the guy in his apartment doesn't seem like a character due the way he vanishes or there will be a plot hole. That truck clearly drawn to kill KC didn't vanish into thin air but only the man did, almost right before his eyes (which got him confused) and then we have Yoon Joo explaining the whole thing about disappearing when she goes from one world to another.  That's what would make sense in my perspective. 

@Bill I agree with the author when he says: "I created him. Therefore it's not murder, it's judgement." Of course KC wouldn't take it so lightly. lol But that's why I believe the killer is someone else entirely we haven't seen yet. 

@Svetlana You got it! Her will or her dad's... that makes perfect sense to me. *-*

(Still haven't had the time to watch Ep. 4 so forgive me in advance if I'm not making sense. T A T)
Hi everyone :D

I've been so busy I haven't been able to post anything. I haven't read all the previous posts either, but I just had to hop on the computer real quick to give @Kate her props. She guessed everything right, and now I'm ttly on board! Lol now I think tht Kate's right about the killer not even having an identity, it's just not important. The father is behind everything, and he had reason to fear Kang Chul because now Kang Chul is gonna come after him. I thought tht would dampen the storyline, but it's not! I love it! Great guesswork Kate!! 

I gotta go now because I'm so exhausted lol. I'm sitting here falling asleep at the computer, so I'll post again later.
Look, if you watch the preview of episode 4, it clearly shows i was right that the father/writer created extra ' character creation ' to try & kill ' Kang Chul ' on the rooftop & with that certain knowledge, it was also the father/writer that created the other character in black, in the penthouse.

Him disappearing in the elevator is PROBABLY because it couldn't complete its purpose of being there, which was given to him by the father/writer, before his drawing device was destroyed that's why he PROBABLY disappeared after the drawing device was destroyed, since he was the father/writer's CREATION, & there was nothing drawn about it & can be after trying to kill ' Kang Chul '.

& the truck didn't vanish in thin air because the drawing device was still operational at the time, which i think gives the father/writer the ' power ' to make something happen in the ' W ' world, so after ' Kang Chul ' forcefully overcame that with his own ' power ' then the story continued on its own & the truck continued on it's own way but didn't disappear because the drawing device was still operational. if you get what i mean ?
Also in episode 4, we know by now that the drawing device is destroyed & along with that so did the father/writer's creation of the truck disappearing as well. what more can i say? xD

also the purpose of the nurse, which the father/writer gave her, trying to kill ' Kang Chul ', as well disappeared, that why she says that she doesn't know why she tried to kill him etc

but you have to remember that this is just my theory, which, i'm certain about so yea xD
@Martin YES! I agree. Every time someone/something tried to kill Kang Chul it was ether out of character or without any context that would fir the story of the webtoon. Because t time ot drawing those scenes Sung Moo did not care if it make sense, he just wanted to kill Kang Chl so he did not give any additional motives behind those characters action. so it make sense that later on when asked, they have no idea why they did what they did, because Sung Moo did not 'give/draw' them a reason, he just made them to it. 
now the question is: since the drawing thingy/device is broken will Kang Chul come back to webtoon? SOPILERS!!! since we can be sure he won;t kill himself in 5th ep even tho preview shows he will try. so now he is stuck in real world without any of the people he thought were his friends, with no identity whatsoever. HE might go after Sung Moo and then what? 
currently at 8 mins of episode 4 so i don't 100% know anything i said is true yet ROFLMAO since it is just a theory of mine xD

EDIT: Damn that was good, can't wait until next weeks episodes now OMFG hahaha
@Martin: Well, episode 4 washed away my hopes and dreams. T A T You're right, everything's clear like water now, I was hoping for too much. *sulks* But just think how awesome it would be if it really was another dimension's Kang Chul behind everything! *-* I'd be mind blown!!!

I got kinda disappointed that my crazy ass theory wasn't real but W is still kicking my feels too high and that ending!!!!!! I YELLED!!! Oooooh, god.
I just hope this doesn't focus solely on KC's revenge and how that messes up their romance from now on or it might become like every other drama...
i'm more curious about the guy who's taking control over the drawings you can see that sometimes the father (who's trying to kill k.chul) is powerless and can't do anything because someone want to save K.chul so there's one savior , one indirect killer (the father) and the other killer . I don't know about the savior but for the other killer i think that like some of you said before it's another k.chul but why? or Son Hyun-Suk the director of the show in Chul's world  and i even suspect his bodyguard but there are many other possibilities can't wait the other episodes!!
I TOLD YOU GUYS SINCE DAY ONE THAT THE KILLER DOES NOT EXIST OMFG HAHAHAHA It just made the most sense... Honestly, I'm surprised how many times I was right hahaha even with Kang Chul trying to kill (doubt he will really die tho) Sung Moo, guessed that too. 

@LyndaKim don't know if you saw 5th ep but it's getting pretty clear that Kang Chul saves himself and he is the one who takes control over webtoon world from time to time. There is no 3rd party here. 
Based on ep 6 and ep7 preview, it looks like the killer is the real "monster" that the father was afraid of. The killer doesn't have an identity, but seems to be the real reason that the webtoon has come alive. They even have the power to come into the real world just like Kang Chul as you can see from the scene with the bikers. I'm not quite where this monstrous creation came from or how it is able to take control of the webtoon, but I'm hoping it will be explained later.
The killer is the yin of KC's yang character, when YJ created KC she was doing it as escapism from the horrible reality of parents in constant conflict.  When a child witnesses parents fighting being oblivious to the child's needs, a child likely feels abandoned and alone.  Unconsciously, a child may use fantasies as a mean of escape because she can't physically escape.  Unconsciously, YJ may feel abandons and angry at her parents so part of YJ's yearning is to be rid of her fighting parents (her family), therefore the killer was created to eliminate family members.  The killer always goes after KC family members.  That's my guess anyway as I watched up to episode 7 at this point.
At this point I don't think there is one. Like Kang Chul I think the killer has just taken on a life of his own. 
@Lotus I think the same. I think it is the first Kang Chul she created. During the latest ep's flashback scene, it showed her creating a character, but that first character did not look like Kang Chul nor was the character's name mentioned. In the final scene, the killer says he is a gifted shooter like Kang Chul. That first character was a shooter. 
Hmmmm I'm also of the opinion that YJ created both the killer (thou she probably didn't intend him as such) and Kang Chul and they both were such strong personalities that they came to life
Well... the last couple episodes had me confused all over again... the killer IS "real" after all. lol Fancy that.
I'm just going to say that i was right again xD the bloody drama even explained how i meant it LOL through his ' hypothesis ' in episode 8 ... apart from the fact he somehow became a ' real boy ' just like Kang Chul :L because of this drama's unpredictability