Author said there will be the end game. So we have two options tbh.
Imo if they still love each other and they changed on their own. Joowon was reflecting his actions and started growing, maturing etc. He didn't persuade Haesoo to come back.
Spoilers
He also apologised. And let Haesoo go. And Haesoo also started reflecting on his own actions
End of spoiler.
So if both of them entered the relationship as changed, mature people. And they would start talking openly about their issues, feelings, problems finally. And they would put much effort to make this relationship work... I don't see why they shouldn't give it a try. It once again it's just my opinion.
You see, I do think you are right in your reading of the situations. We’ve been given more insight on Jowoon and Haesoo’s relationship that it’s undeniable both of them have feelings for each other, they’ve had them from the beginning and they sincerely cared (in their own way?). At this point, I can’t help but acknowledge that it seems almost inevitable they’ll be endgame.
BUT (and here comes the regrettable but as well as the part when I talk about MY personal stand on this) ... first impressions have a lot of power. And I reaaally disliked Jowoon at the beginning. I can’t even justify why right know because it’s been so long but I’m pretty sure everyone who had issues with him already listed their grievances against him multiple times before, and mine probably coincide with at least one of those. Of course, we’ve come a long way and we now understand more about him and his actions, motivations and difficulties because the author gave him a more sympathetic light; now, I don’t dislike him as much as before, but there’s a little irrational part of me that holds to that unrelieved anger and selfishly wants him to lose.
And that’s it.
Like, there’s not a single justifiable leg to stand on my desire for not letting Jowoon and Haesoo to get together again (because I can see that’s taku has stopped being the ideal alternative that it sort of seemed before and doesn’t even get to be the preferable one anymore) and every other reason I give is going to be a nuance of this or my personal preferences, that probably influenced my initial dislike in the first place. Still, I’m willing to risk a little bit of pairing dissatisfaction because this is a very interesting story: all those underlying emotions, the whole characters’ dynamics and the little details make it worth it really.
Anyway, I thought I’d give you an honest review on my take, because I liked your post and i thought it’d be nice to share. Sorry if it was unnecessarily long (or just plain old unnecessary lol)
I just want to explain MY point of view.
I'm pointing it at the beggining so no one will accuse me that I believe I'm infallible (of course I can be mistaken because it's only my own interpretation).
Let's start with the fact that in stories there are some elements which aren't stated openly. All of us can remember (I hope) literature classes where we analysed, interpreted different texts, books, poems etc.
Some things aren't and often don't have to be said openly.
Feelings can't be proven like mathematical proof or idk blood test. It's not something material, physical. But how do we know that someone loves or hates someone else?
By their actions, by their reactions.
How do we know mother loves her child? She has to say: "I love you?". I don't think so. The actions are enough (for me at least). Her smiling gently, helping genuinely, asking about their day. Small gestures here and there.
As I said in previous comments I can be mistaken but I think Haesoo has romantic feelings for Joowon.
1. He has stayed with Joowon for years although it impacted his relationship with mother, one of the most important person in his life...
2. He cares and worries about Joowon deeply. He was completely shaken when Joowon wrote he hurt his hand. When the affair appeared he abruptly interrupted important discussion with his mother and went to clear Joowon's situation.
3. He was jealous not long time ago.
4. He desires him physically.
5. He thinks about Joowon, his wellbeing, their past while being with his new partner.
All these things added together CAN hint, symbolise he has romantic feelings for Joowon.
Spoilers
Add to all of this the newest raws (chapter 87) it's imo rather clear Haesoo still loves Joowon and didn't move on.
I guess he "broke up" with Joowon.... Because he just didn't see the future for them .... He was scared, afraid. He wanted to choose something realistic, accepted by society, his mum. In earlier chapters it also looks like Haesoo hoped Joowon would marry a woman, choose simpler path.
Their relationship has stayed the same for years. Their feelings unspoken. He wanted the break. He couldn't stand that situation anymore. But imo it doesn't mean that he doesn't love Joowon anymore.