Idk about you but from my conclusion seoin kinda resent how yeongwoon leave him 10 years ago without explaining anything. Pretty much he thought yeongwoon just other people who leaves him
Yeah ik that, I was saying seo-in needs therapy cause he's doing some inexcusable shit and is obviously not in a good frame of mind idk how angry he had to be that yeongwoon left him it doesn't excuse raping him and fantasizing about it either or sending that one brown haired dude back to his weirdo ass cousin, and he's definitely not going to face consequences for these asshole actions so the best I can hope for is that he goes to therapy and gets a bit more normal
the answer to your question its bcs of he was obsessed with yeongwoon, and yeongwoon are possessive with seoin that’s why he willing to have seggs with seoin cause he doesn’t want seoin to have seggs with someone else, and i think seoin character development will be around when he finally know what Yeongwoon been through 10 years before that Jaewon abuse him and how guilty he will feel
They were so sweet as kids why is their relationship the way it is now. damn it like after seeing this I just wish they could be happy together but seo in seriously needs some therapy