Could someone tell me, why were Haesso and Jowoon in a fuck buddies relationship for so lo...

It's fuckin yaoi nothing makes sense and there's always tension(๑•ㅂ•)و✧

i think it was bc they both thought it was only one sided. so they didnt want to tell the other how they rly felt, and just kept seeing each other casually.

what i mean by one sided is the romantic feelings they felt

Basically first joowon did it to protect haesoo, to keep his parents from.separafing them, he wanted to be besides him in whichever way possible. If they became lovers, they could break up too. Haesoo was holding a grudge since their high school days when.joowon told him to not fall in love with him because he won't fall in love with him. Though he wasn't aware joowon had already liked him since the .moment they met. Their parents marriage situation was another thing that kept them from dating since if they decided to get married, they'd really become brothers. So being fuck buddies suited them in case things turned out in that weird way. I personally liked it when haesoo realized that they had already been a couple since high school and after they reunited but they didn't explicitly said it out-loud.

So Jowoon wanted to be fuck buddy because if their parents separate them, it's less of a big deal, since they wouldn't be dating, and they could still be brothers? OR did you mean Jowoon just never wants to break up with Haesoo so the best option is never date?

Both I think. He didn't want to be separated from haesoo - that's why he repeatedly saying "I'm your brother, your friend, your lover" he didn't say the last part - I think they were both afraid of taking the next time and were using the circumstances and their past misunderstandings to avoid confronting it because before taku, whoever haesoo "dated" or mostly had sex with, joowon knew he wasn't serious. You should re-read it to really understand their relationship. After re-reading it, I understood so much more than just on my first read through. Their relationship is really beautiful and complex and tragic. You can't pinpoint exact reasons - since they're so inseparable from there past. The bottom line was they really fucking loved each other to death but were afraid of saying it for a lot of reasons.

ALSO I think joowon wanted to really date him for real - he flirted with him and bought a diamond ring yoooo probably propose to him but taku had already interfered between them.i personally really hated his character overall - and re-reading it, i think taku was actually the one who was treating haesoo like a fuck buddy. There wasn't a single scene where they were just chilling or not working or having sex. Even when haesoo was sick, he was fucking him nonetheless. Joowon and haesoo'a relationship had so much history and complicated dynamics and real painful tragic and fluffy moments. You should reread it.

Because technically they couldn't date because of their parents but also at the same time they couldn't stay away from each other because they went through so much with each other. They even took away each other's viriginities.

But didnt their parents separate? And when that happened it didnt change their relationship

They separated because of these two having a sexual relationship...but they were planning to be marry again after 10 years but these two were still the issue.
Please read the manga again... it seems like you don't know how the story progressed or aren't interested in it for some reason.

I personally think it's quite annoying. They both wanted to be serious but they avoided it as you said. Which is understandable when their parents were together, but not really justified when their parents broke up(unless im confused and their never broke up???)

Also, i think it's pretty dumb Heasoo started having sex / dating other people. The whole "i want to forget him / i want to stop loving him so i'll try other people" is such a bad cliché.
Why even date someone you aren't interested in? And if Haesoo was interested in them, he could get serious.
And why have sex without strings with other people when he has Jowoon (or was it hard to meet Jowoon?)

And it lasted so long. For something quite simple.
This story is pretty much "the MCs didn't know their owns feelings, they didn't know what they wanted, so everything is chaotic until they realize the obvious, get together"

AT LEAST, it was also Jowoon's fault. Most of the time, it's only the uke who is the cause of the drama in these triangle romance, but in this one,the seme was part of it too. So it's less annoying, since both sides are doing the same.

Thanks for replying <3 . I'm not saying this is a bad story, but stories whose drama is all about figuring out their feelings isn't my cup of tea. I thought maybe there was another explanation but you made it clear, thank you (ﾉ≧∇≦)ﾉ ﾐ ┻━┻

And when the parents separated, they had the options to get together, as they were no longer brothers. But it didnt change their relationship at all.

Or did the parents told them "ok we will separate for now and get back together in 10 years so stop this relationship"?

No, that's not it. When they reunited, Joowon told him he wanted to kiss, and haesoo was hesitating, thinking that he was the only with romantic feelings so doing it again with joowon would hurt him. Joowon said later that he said "it's just like before, for fun" because he was afraid of telling haesoo that he was in love with him since back then and he had lied before and haesoo would run away and abandon him if he knew how seriously in love with him he still was. I think this is a good lesson on how hung up people get on the past that they ruin their present relationship because of them. Clichéd as this story might be, but haesoo and joowon's relationship is very realistic, that's why it's so frustrating. IRL relationships are rarely so cut and dry, even if people have all the reasons to be together, they don't go ahead with it. Fear of commitment, fear of rejection, fear of breaking up.

My point is, Jowoon's fears wasn't valid after their parents broke up.

If losing Haesoo was Jowoon's fear. Then staying as sex friends was actually much more risky to lose Haesoo.

And if he was confident that Haesoo would not leave him as sex buddy, he should have had the confidance to believe the same about dating.

He thought haesoo abandoned him because he broke his heart before when he told him to not fall in love with him. He didn't know haesoo stayed by his beside the whole night before he left...he was angry he was abandoned by him without a word. If you read the latest chapters, you'll see joowon told him he wanted to keep it casual so he doesn't run away and abandon him once again and how he resented him for doing that to him once again. And when they were having the epic breakup fight in ten hotel room, joleon was breaking down because he was again abandoning him but now for someone else. It is really heartbreaking. Please read the manga again to understand it. I think you really didn't get what the story actually is

If he thought he was abandonned because he told Haesoo "dont fall in love". How is staying sex friends gonna stop Haesoo from leaving again???? That's repeating the same mistake. I'm sorry but that doesn't explain anything.

Look, i get that this is a story about "omg let's never date so we will never break up" / "i dont want to lose but i dont have the confidence to take a step forward". But that's quite dumb when Jowoon knows Haesoo loves him

I'm sure he realized he was being a dumbass for keeping haesoo at a distance - you can see him reflecting and growing up enough to realize it. That's why I said you need to read it again - joowon says "If I could go back and rewrite our story, I would. And he would tell him he loves him and he'd never let him go."
This story isn't about making perfect decisions but making wrong choices and then growing from them and making things right -
What you said, if that happened, this story wouldn't exist. Rarely do people make the right decisions in life, more so in a romantic context, the feelings and the anxiety of losing people because either you feel too much for them or don't feel enough is a real thing.
If you don't like the story, because probably you didn't get it, then there is no need to look for explanations. That's just what I think.

Of course we all do wrong choices.

I am just saying that in this case, the mistake is taken to the next level to the point it's ridiculous. And I know yaois is all about ridiculous characters/ineractions. I just personally dislike when it is used for serious drama.

Also I do understand what happened, you are the one who turned around in circles, trying to justify why Jowoon made this choice with stuff that were irrelevant.