
ok so this is what i understand from rereading this again
so moonhyuk is either extremely loyal to chagang (his old owner) or he loves him. or he's obsessed with him. stuffs happened and he got sold to boxing illegally. and then yeonjin bought him. the way yeonjin acts is like chagang like fucking other men in front of him, red ropes, his eyes while having sex, etc. i guess maybe that's why moonhyuk wants to choke him (because chagang likes to be choked?) so moonhyuk does the same to yeonjin. he unconsciously see them as the same person. that's why when he got drunk once, when he was fucking yeonjin, he mistook yeojin as chagang
the last dialogue, "i look like our father" he was talking to the old him. the kid him. his mother told him to be like the father, so he copied his father, including fucking men. but he realised by fucking men, his father is gonna be disappointed in him, so that's his way of revenge. the way he's gonna destroy his father is him destroying himself. and he also grants his mother's wish of yeonjin will be like his father. so it's a win-win situation. he satisfied himself and his mom
chagang died because of political affair or some shit? there was a flashback of chagang fucking with a man with a scar across his mouth. and then in the present time, there was a time when the dude who wanted to fuck yeonjin (idk his name, like the other dude yeonjin is fucking other than moonhyuk) called a man with the same scar across his mouth, as "uncle". so right now yeonjin is also indirectly involved with the man who killed chagang. and based on chapter 1, i guess yeonjin will die because he got involved with the man (idk if he literally dies or just an act since there's no dead body)

I'm honestly confused too and my understanding might not be what the author wants to portray but it's just what i understand from the manhwa so far
and the author is known for making confusing af stories lmao. I read blood link and tales of yellow dragon and most of the times i lurk around the comment sections reading people's explanations on what's happening hahahha

i don't think it's exactly a secret that he's fucking men. so yeonjin fucked moonhyuk at the hotel on his son's birthday, and the other dude met him the next day and said "i heard you were fucking with moonhyuk at the hotel". yeonjin didnt even say he was gay, but the dude knew. so in return the dude asked to fuck yeonjin as exchange for information. i hope you know which dude I'm talking about cause i forgot his name hahahaha
this is my opinion, yeonjin's son will be shocked that his father fucked men, but i dont think he's the one being hurt the most in this story. yeonjin fucked men, and his wife is okay with it. technically he's not cheating or doing anyone dirty. and he's doing a favour for his wife, and his wife only cares about their son, so both sides get what they want. i think the favour that he's doing for his wife might be related to yeonjin's father as well. maybe both of them want revenge on yeonjin's father? because in one chapter yeonjin's wife said she didn't like her father in law (yeonjin's father)
meanwhile yeonjin's father cheated behind his mother's back, causing his mother to kill herself.
what he's doing is similar to what his dad is doing, and there's a possibility that he's doing this because he wants to copy his father purposely. his mother keeps on saying "be like your father" so he did what his father did. that's why in the last dialogue he said "i look like our father" with a smile

probably a coincidence? he didnt act 100% like chagang but the little things might accidentally make uke looks similar to chagang in seme's eyes. seme is obsessed with chagang, and chagang is already dead, so those small resemblance mean so much to the seme
for the red ropes, there's a possibility that the uke knew chagang likes to wear red ropes while the uke trying to dig chagang's information. there was a part when the author showed chagang with his men and he wore red ropes underneath his shirt. he's probably a kinky shit and wore it outside the bed lmao. so people knew chagang likes red ropes so maybe the uke suggested the red ropes to the seme to provoke him? uke maybe has feelings for seme already but he's pissed at how seme is not getting over chagang. so he provokes seme by doing what chagang has done before. he did say he was pissed off with chagang and laughed because "i will never win against a ghost"
for fucking the other dude, honestly, i would like to think that uke does that as a revenge lmao. seme fucked him drunk before this and mistook him as chagang. uke was pissed off about that so he got his revenge by fucking another man and asked seme to watch. or he can't get hard/cum without watching seme so even though he's fucking another person he won't be able to get off. maybe that's why after he fucked with the dude before this at the hotel, he asked chagang to come and fuck him afterwards so he can cum since the previous dude can't make him hard. idk

I still think it's weird for the uke to sleep with that man.
Because : how did the uke know the seme would be pissed about that (he knows the seme don't like him so it's weird to assume the seme would be jealous). And if the uke is doing this to trigger the seme's past, what makes the uke think that this will eventually help him to overcome Chagang in seme's heart.....

well seme didn't show much expression and just went along with things at first. he didn't show what he's thinking. the uke probably use chagang (since seme is obsessed with him) to provoke the seme so he can see more of what he's thinking/feeling
personally if I'm the uke, and I'm already attracted to seme, i would do the same. seme acted like an expressionless dog and just followed everything and it pisses me off. so in order to see more of what he's thinking, and see other sides of him, i would provoke him using chagang as well
idk i think it makes sense for him to sleep with the man. he thinks sex doesn't mean much(probably) and he doesnt have any commitment either. he called in the seme either just to provoke him for fun (to see his reaction) or he just couldn't cum without seeing the seme (he didn't look like he enjoys the sex with other people and wants to get it over with)

I understand what you mean. But then we are going back to my 1st comment : why/how does the uke KNOWS that sleeping with another man would trigger the seme.
So it's really weird that he suddenly decided to sleep with that man. I'm not saying it's wrong, but I just don't see any reason for the uke to suddenly spread his legs like that. (Clearly he isn't doing this for the sexual pleasure).

hmmm. idk if he's having fun about it or he legit knows it's gonna pisses the seme off. i guess we're gonna wait for more chapters. this author is known for making confusing af stories. I've read tales of yellow dragon and blood link (both by the same author) and i only understand on what's happening based on what people comment lmao. the manga itself is hella confusing
i just explain to people based on what i understand and the impression i got from the characters. the raws are only about to 30 chaps i think, so we still don't know much of what's happening. the latest chapter has got yeonjin meeting his father (〜 ̄△ ̄)〜

I disagree about the uke doing this because of the info. The uke offered the deal on his own and nothing pointed out that the seme would only accept sex. And worst case, the uke could have just hired someone else. I know yaoi logic is stupid, but it feels more likely the uke is doing this because of something else (and as we just saw, he is a bit crazy so it might fit his character to have some weird hidden agenda).
I never said he did anything wrong, i'm just trying to understand what's his goal.
Also you might be mixing 2 mangas? You used names that doesnt seem to fit
ahhhh the misunderstanding between them is finally solved!! breaks my heart to see them apart :(