End Game Theory

Theories:

1. Yijin is dead. (Mom must've visited the grave last month)
2. Hee Do never married. The kid's mother is Yu Rim (who is also dead).
3. JiWoong eventually realizes that he actually is in love with his best friend ans they'll be endgame.

Rationale:
Regardless of whether YJ/HD broke up or whether he died, I just don't see HD being pregnant at the age of 25. Not when she fell for YJ at 21 and definitely not when she'd be in the middle of a blooming career. The child belongs to someone else and the only person i can imagine her doing this for is YR.

 Ivy:

3. I'm hoping they don't date because as much as much as I love friends to lovers not all close friendships need to go that way and it would be nice it this one didn't. 

but i feel like they already like each other and there's def gonna be romance 

 Roro2022:

That's the feeling I got too. And there's something about the way their stories are progressing. Reminds me of korean web dramas having childhood friends to lovers plots. I'd feel a bit differently if the JW-YR romance had a solid foundation but from what I understand JW likes YR because of what she represents, without actually knowing her. 

She's always there for him so it's obvious why he starts falling for her, he lost everything and she's the only person who's cheering him up knowingly and unknowingly they're giving each other strength so that's the best kind of love in my perspective 

 Roro2022:

Theories:

1. Yijin is dead. (Mom must've visited the grave last month)
2. Hee Do never married. The kid's mother is Yu Rim (who is also dead).
3. JiWoong eventually realizes that he actually is in love with his best friend ans they'll be endgame.

Rationale:
Regardless of whether YJ/HD broke up or whether he died, I just don't see HD being pregnant at the age of 25. Not when she fell for YJ at 21 and definitely not when she'd be in the middle of a blooming career. The child belongs to someone else and the only person i can imagine her doing this for is YR.

i dont think yijin is dead early bcoz hee do's mother said he looked really young or like a kid  back then , that means he must have been at least alive in his thirties  bcoz they know how he looked like as an young person ( that's why the comparison)
and hee do said he "was only" 22 back then , that means must have aged.
he might have died in his thirties or left hee do in his thirties.

A part of me (the optimistic one) also feels that this might all be just a trap and they actually have a happy ending. I understand if they'd want to "warn"  us about them not ending up together but it's just Episode 4 and they're already "too out there" with these hints. If they so desperately want us to believe that they don't end up together (desperate because within 4 episodes we've practically been given a confirmation that they won't end up together), then perhaps they will in fact be together.

1. They've used different actors to portray the older versions, perhaps to demonstrate how different the characters look after aging. Maybe that's why the daughter didn't recognise him? We've seen that happen in 18 again. 

2. Maybe he changed his name after adopting a pseudonym as a reporter? Or because of some other reason? Everything else will make sense if this point is proven right. 

 Roro2022:

Theories:

1. Yijin is dead. (Mom must've visited the grave last month)
2. Hee Do never married. The kid's mother is Yu Rim (who is also dead).
3. JiWoong eventually realizes that he actually is in love with his best friend ans they'll be endgame.

Rationale:
Regardless of whether YJ/HD broke up or whether he died, I just don't see HD being pregnant at the age of 25. Not when she fell for YJ at 21 and definitely not when she'd be in the middle of a blooming career. The child belongs to someone else and the only person i can imagine her doing this for is YR.

1. Yi Jin is not dead. Because  Hee Do's mom said she met him last month.  He surely did not die in the meantime. But why they are now like stangers and have been since years?

2. I don't think Hee Do had a daughter out of wedlocks. Huge mystery about her father but it is probably not Yi Jin  as I don't see any reason why he would have stayed away from his own daughter.   In any case, the fact that Min Chae sees him as her mom ex and not her dad suggest he is not her dad.  Unless her mom lied to everyone for some reasons like Ji Jin married someone else...

3. Agree. Probably Ji Woong and Yu Rim are secondary couple endgame.

 Roro2022:

Sorry, I guess this got confusing. This specific point is about the second leads, not the main leads. My theory was about how the second male lead might end up with his best friend. 

Ohh sorry i got confused as well, right I'm curious about whats going to happened to those three

 Roro2022:

A part of me (the optimistic one) also feels that this might all be just a trap and they actually have a happy ending. I understand if they'd want to "warn"  us about them not ending up together but it's just Episode 4 and they're already "too out there" with these hints. If they so desperately want us to believe that they don't end up together (desperate because within 4 episodes we've practically been given a confirmation that they won't end up together), then perhaps they will in fact be together.

1. They've used different actors to portray the older versions, perhaps to demonstrate how different the characters look after aging. Maybe that's why the daughter didn't recognise him? We've seen that happen in 18 again. 

2. Maybe he changed his name after adopting a pseudonym as a reporter? Or because of some other reason? Everything else will make sense if this point is proven right. 

Yes I also think that the future scenes are a trap as it would be too early to divulge or make people know what will happen in the end especially about the couple since a lot would be anticipating the romance. They might just be stirring our interest for us to look forward every week.

I agree with your points the parents might not exactly look like the way they are in the future and Baek Yi Jin might have entirely change his name for a lot of reason as do many people maybe for luck, good health whatsoever if he is superstitious. He might have also change his name due to the fact that there are a lot of creditors coming at him. It might be one of the tactics his dad have. Maybe the Kim comes from her mother or a relative that will take him in.