
Haesoo and joowon both love each other but just can’t tell each other nor the public, because of work and their parents. That’s why haesoo tries to distract/forget himself and his feelings by playing around with taku

Um...no
The reason the relationship is so fucked up is the fact that they both played games with each other, they were immature teenagers in a taboo relationship. Now, Jowoon doesn't listen to Heasoo. And Heasoo became a pushover. Heasoo has the blunt end of the relationship. His relationship with his mom is ruined, he doesn't have the career he deserves. He's suffering in the relationship and Jowoon isn't. Heasoo is suffering so badly that he has anxiety.Jowoon doesn't want to change anything. He's comfortable with the relationship he has with Heasoo. Coming by to fuck him whenever he wants and leaving. They've always been like this--Jowoon even said it. So, no a simple, being on a down low relationship isn't the problem. It's the fact that one is suffering and the other isn't and the other doesn't give a fuck to change or even listen l.

What you say might be true, but haesoo meeting taekyung will forever change him too. Haesoo might use taekyung at first but I’m pretty damn sure haesoo will develop feelings for taekyung too. This will change the relationship between joowon and haesoo as well when joowon finds out haesoo has someone special as well

I think so too, everything except for the playing around with taku part. He loves taku too, i think its because he gets the treatment he wishes joowon gave him. But its doomed because their relationship is so complicated that not even them themselves understand it. So taku gives haesoo a feeling of comfort and support while joowon makes him feel lost and alone :(
Finally
He really deserved to be happy