Looking For Yaoi Manga

Not talking about polygamy. But people who ask for open relationships, aren't they basically just asking for permission to cheat? Or like do open relationships even work even where both of them come up with it together? Someone please explain, because I cannot comprehend the thought process of people in those relationships.

It was a manhwa. The main characters meet in high school. Gong was a total nerd, canonically ugly with glasses and all. Su was the cool guy, played sports. Backstory on them, Gong had a good childhood, has a supportive and loving family and an older brother who cares, but Su had it rough, he was the product of an extra marital affair, him and his mother were kept hidden by the father, father was abusive (if I remember correctly)
Now the story: They meet in school, idk how they met but Su started to take Gong's gym jacket before going to play soccer. Gong had crush on Su, so he would give his jacket, no questions asked. They started talking and their relationship developed. Then, Su's mother dies(?), and he didn't go to school for a while, Gong grows worried. Later when Su comes back, their relationship develops.
Another twist, they "make a friend", the girl starts following Su around, the girl has a cousin/brother who lives abroad.
Something happens and Su runs away. In foreign, Su meets that cousin/brother outside of a party, they hook-up, it turns into a relationship, a toxic one with a lot of abuse towards Su.
When Su finally runs away, during one of their "off periods", he comes back to Korea, he meets Gong in a reunion, they reunite.
I remember the story but I don't remember the names of the character or the title

Uhhh so it’s like really weird so bear with me please…
My friend described it to me during class and I don’t remember much but I think its about a foreigner who goes into a tribe or sum? I just remember there was a scene where the foreigner goes infront of a dark place, the mc said AND I QUOTE (actually prob not 100% correct dialogue but it was about flying underwears) “ahhh! Theres flying underwear coming at me!”. It was because the people of that tribe are dark skinned, that’s why he said that but uhm… If you know it than pls tell me!(⌒▽⌒)

I'm looking for a manga, I don't really remember the details so some of this might be wrong. I think both main characters were in the same high school, their families were rival (traditional Japanese) theater groups and both guys were actors in those groups (I think one group was more traditional than the other and they were looking down on them for that?). One of the guys has a falling out with his family, and they end up running away together and form their own theater (or something). It might have been a oneshot included in some other volume or it wasn't finished because I don't remember what happend after that.

It's not "Hanakoi Tsurane" btw. Thanks for your help!