The biggest one would have to be the promise Oh Sung Moo made to the killer, telling him that he will turn the killer into the main character of 'W'. But Oh Sung Moo had only made the promise only because he was about to be pushed over the edge of a hotel roof located in the webtoon world. Knowing that 'real life' characters cannot be harmed in the 2D sphere as long as they are not major characters, Oh Sung Moo really had nothing to worry about even as he teetered precariously on the brink of (what he believed was) sure death. But at the time, Oh had no idea how his own webtoon worked; thus, he ended up making that foolish promise...aaannd ended up breaking it and pissing off the killer. Good job. Well, not really.
"I'm sorry, what?? You killed yourself but you're still alive??"
Thankfully, Chul, being a brilliant man of many talents, finds out a way to get rid of the killer in the webtoon and return Oh's face safe and sound. Not so thankfully, we don't yet know if Chul's plan will work. There are still four remaining episodes, and despite the reunion of Yeon Joo and Chul at the end of the episode, I get the feeling that the happy ending won't come so easily. I just can't rest until I clearly witness the permanent demise of the killer, who, for unknown reasons, wants desperately to be the webtoon's main character.
"Okay, so, I'm technically not real, BUT, we can still get married and live happily ever after!!"
I wonder, what motive does the killer have to be the main character in 'W'? His entire existence is nonexistent, serving only as a part of Chul's painful history. So the killer's purpose is simply to give purpose to Chul's story. Other than that, the killer is pretty useless. When he gains 'awareness' after meeting Oh Sung Moo, he is able to travel back and forth between the real world and the webtoon world, and in the process, he learns that he never existed in the first place. The killer then sets out to give himself a physical form, achieved only after he steals Oh's face. And then what? Chul is now "dead," and soon, (or so we hope), the killer himself will be killed as well.
Hide yo wives and hide yo kids
All this rambling leads to the my big question: who will be 'W's lead? Chul is gone and so is the killer, who was slowly turning himself into 'W's main character. Further, the webtoon continues to possess a life of its own, drawing itself despite the creator's current indisposed condition. The whole time I was watching this episode, I wondered whether the events progressing in the "real world" and in the "webtoon world" were also being drawn out by an unknown, greater force. I mean, someone's gotta be drawing out the scenes, y'all. That is the biggest question that the drama needs to address.
We saw in the earlier episodes that any scenes that Chul was involved in, they were automatically included in the webtoon. That was when Chul was still the lead in the series. But clearly, 'W' is now missing a lead because the lead is "dead" after he separated his "real world" self from his "webtoon world" self. I'm just going to presume that Chul's "real world" self is not a part of 'W's story and neither is the time he spent with Yeon Joo. I suppose that's what Chul meant when he said Yeon Joo and he will get the happy ending they wanted? The happy ending can't exist in the webtoon world because both Yeon Joo and Chul broke the fourth wall and their story can't continue within the confines of boxes lined with black. Wha...what...just WHAT IF...Soo Bong is the mastermind behind everything?? Now THAT would be a twist ending.