Theories [SPOILERS]

I agree with most of your ideas and love them, my mind made similar theories too. The game is an interactive AI that has access to people's consciousness, I also think that the cafe was the stage everyone is "fully linked" to the game, the rain and guitar started there, so the answer to ending all that could be with emma there. 

I also believe se joo is not dead, the game was being played as it is its purposAfter the surprising news Yoo Jin woo got, he found himself back in granada asking Jung Hee joo for help. In the light of the new information, things started seem more suspiciouse but maybe it can't kill it's creator for it being programed in it or the thing he took out of the bag, I am not sure yet.

One thing for sure jin woo should stop the production of this game. But then the preview says otherwise

Someone said that a jumanji like could be a theory too.

Huh, I really like the Emma theory. There's definitely a connection between her and Hyun Suk as the music cues his appearance. 

Though in the latest episode, Jin Woo wants Emma to be rid of; wonder how this will develop. 

Good point you made with Emma, rain and music. Maybe it is something about relating the game to a real person and have true feelings about it. Maybe Jin Woo fell in love with Jung Hee Joo just there standing in front of Emma - he was amazed really :)) Like wise when he became enemies with Hyun Suk or allies with Jung Hoon the feelings were real. Maybe because of that they could not break that alliance.  And also Jin Woo had the will to kill Hyun Suk although he didnt know he was actually killing him.

After new eps I guess it's time to update my theories lol Coz shit happened and it's worth talking about it but this time I will divide it into setting and specific characters to make it as clear as it can be:

setting: 1st I want to say I am pissed they are not consistent about the rain and "Memories of the Alhambra" as being an omen of Mr. Cha showing up. There were a few scenes where there wasn't either rain or music aspect when they fought.

 I like how picky they are with what to show from the future. They gave us some scenes at the beginning that didn't happen yet, so we kind of know in what state we will see Jin Woo, but they don't really answer the important questions "why" and "how" did he end up like that. When I saw in I think 2nd (maybe 3rd?) ep, there scene in the train where Jin Woo was fighting with gun and limping on one leg I assume he just got hurt. Now we know it's permanent disability. I like those type of details. 

Emma: I am starting to think she is not that important after all. And what I mean by that: she is not her own character. She is there to be a link between Jin Woo and Hee Joo. They did nothing to even hint she might become active participant in the plot, rather she is just a tool. I will be disappointed if Hee Joo joins the game and "become"/takes over Emma's character. I would rather see her even being just NPC but separate from Hee Joo and see how the dynamics would work out. I also gave up on the theory that she is the brain of the game even tho I still like the idea hahaha

Jin Woo: he's just so broken I love it. Not many theories about him since his actions and reasons are well presented. He wants to keep developing the game, coz without the game he can't find Se Joo, but he does not want the game out for the public since it was confirmed it's not only him who can get hurt during gameplay. 

Hee Joo: If I saw one more person who says she is just another weak female lead I will break some jaws lol Showing your emotions does not = being weak. She is strong af. She was the head of the family since she was really young. She basically raised her sister. Does she cries a lot? Of course she does, she was in constant fear for her future and future of her family because of the debt, she had more than one job to make sure they had money for living. Girl was exhausted. I would cry way more than her. The point is, she cried but still kept going and that's what being strong really is. Some people have really unrealistic and stereotypical ideas about what being strong means. 

I still don't know where the plot leads her tho. I assume she might get into the game next ep since the only way to contact Se Joo that we know of at the moment is via the game? 

Se Joo: he sure killed Marco. Marco probably wanted to steal the money when they sell the game or just steal the game itself and sell it to Mr. Cha even tho Se Joo was not too happy about that idea (? he did call him a bad person after all) . Se Joo quite obviously wasn't 100% sure if he wants to sell it in the state that it was right now. They fought in the game, Se Joo was on higher level, kill Marco, and same shit happened that we see now with Jin Woo and Hyun Suk. That's why he was running away from "nothing" in 1st ep. 

MAYBE he got himself into the medically induced coma (since we know you are safe when you sleep, tho how would he be able to get into coma is a ? lol) and left clues about where to find him and what is going on for the player who reaches his level (since that would mean you know the mechanics of the game well and you would be useful and not just get yourself killed). So the message from Master is not from Se Joo in the presence, but rather it was left by him in the past? BUT that does not make much seans since we saw his body was lying on the ground on the train station but only in the game reality. So the idea he is trapped (or he willingly locked himself) in the game is still valid. Maybe if you become 100% part of the game not just a player you can't get killed? You just come back like Hyun Suk? But then in the preview he called Hee Joo so I am just confused with what is going on with this kid hahaha 

Cha Byung Jun: at this point I don't think he is related to the game part of the plot. He is just a di*k who cares more about his reputation and firm than his family. 

Game rules: I went back to the end of 2nd ep where we had that train gun fight scene that did not happen yet in the present times of the plot to get more into about what will happen in future eps, and holy shit I am confused about it all and rather than theories I have some questions:

1. Why were people reacting to the gun fight as if it was really happening? people would obviously react to Jin Woo just doing some random stuff since they don't see the gameplay, but they were running away and screaming as if they were really scared. why? were they all NPC? that does not make sense since they would only show up when he got dragged into the game... 
2. Who was the last character that had Jin Woo at gunpoint and why does he not feel like NPC at all? His eyes were, alive? Also it felt like Jin Woo really did not want to lose to him, and if he was NPC that would not make sense. He would get killed in the game, lose some (probably not that many) points and get back to his journey to Granada. He just seemed really desperate in that scene, as if he felt like he was really in danger. But up till now only other players who turned into NPC after being killed in the game can hurt him. WHAT IF IT IS MARCO?! What if Jin Woo found Se Joo, they formed alliance and now Marco can hurt Jin Woo too. And what would explain why Jin Woo took the match so seriously, since it was truly life or death situation. 

As for the game rules that are "confirmed" not much happened: if you form alliance with other player, they are put in danger and can be killed too. That's basically all the new info we got. 

also: THANK YOU WHOEVER WAS PATIENT ENOUGH TO READ IT HAHAHA I wrote a whole essay. But I am truly really excited about this drama. 

It is funny that I also checked the end of Episode 2 today trying to figure out what was that all about :D That flash forward is 1 year ahead of Jin Woo's introduction to the game, but as of Episode 8, havent one year already passed ?? I'm all confused about it.

I think other people reacting should be NPCs, because there are also not reacting people.

 About "the last character that had Jin Woo at gunpoint" I don't think he is Marco because his body figure is different. Maybe he is a user, those blue eyes  could be due to the lenses.

By the way I dont think Marco was killed by Se Joo, his body was found in the woods, was there any time gap for Se Joo to do it? (I need to watch those Episodes again)

And I have a question about Se Joo. The last time we saw him he was so afraid being chased and was acting like a victim but he is the Master in the game and must have many weapons. Why didnt he fight back like Jin Woo?

@kate i am also very hesitant about Emma, and if it wasn't for the sound of her guitar being evolved i wouldn't think of her being anything other than a way to remind jin woo of hee ju (since their time with each other is too short) and increase her screen time cause the difference is clear. 

for me i think that se ju definitely killed Marco maybe they met trying to finish the game before they sell it and had a fight that led to this. we already know that marco knew too much about these two CEOs and even their private number, i bet he got the lenses, so things with him were sketchy. i doubt that see ju knew about such flaw in the game from the beginning cause that would mean he killed marco deliberately and that mr. cha knew about it which would explain a very important part for me which is se ju calling him a bad person on the phone.. it makes no sense unless he heard something bad from him.    P.S if mr. cha knew about such a flaw it would mean he was trying to murder jin woo knowingly. 

the game had a secret we don't know, the physical disappearance of se ju is strange and the thing he took form his bag must be important. 

@Kate

"So if Se Joo did not kill Marco, why would Marco's NPC target him?"

Simply because they were "enemies" for fun in the game ?