I agree that simply communicating would solve most of their problems.
The point made by this manhwa is, none of the sides in KangJeon relationship tried to communicate with the other.
While Jeonghan didn't voice out his fears and insecurities, Kangwoo didn't see anything wrong with what was going on with Jeonghan in 8 years.
That's why their relationship got fucked and that just sometimes happens, even after 8 years.
And no, having sex after breaking up with someone isn't cheating. Sometimes it's just a way to cope with something.
They wasted their relationship for 8 years. Too bad but the day Jeonghan broke up with Kangwoo is puzzeled by it wanted to make it up for him cause he thought it just mere trantrums or what. Then jeonghan trying to comfort himself with Gyung tae using other person emotionally and pysichally is not really good in relationship. Hsyt being lack of communicating is truly troublesome. Having sex with another for me it'still counted cheating
It triggered my mentality and my heart hurts. Like WTF! IF HANNIE just been open towards his feeling to Kangwoo and do same thing too. They just COMMUNICATE AND TALK ABOUT their problem properly then it's done. I hate it when for 8 years in their relationship suddenly broke up with him without any reasons to explained everything. And the next few days having SEX with Gyu tae?! For real Honestly ISN'T SOUND CHEATING!! AND UNFAIR FOR KANGWOO
his still hurting trying to overcome thos pain and there Hannie was Having Sex with gyu tae made sick!