You and I have the most opposite opinions about this lol. I didn't mind the whole he's dating his friend's father because said father and son had been estranged for centuries at that point. Gunchan never actually saw Elian acting fatherly towards the ml, and near the end he even mentions how Elian didn't really care about the ml. Gunchan NEEDED to end up with Elian. The whole point of his character is to humanize Elian and make him understand why his son is the way he is. The story would have ended differently if Elian didn't fall in love with Gunchan. Definitely wasn't stockholm syndrome either, Gunchan's too smart and self aware for that.
Elian's character is what you would expect from a vampire who has lived for centuries. What is some insignificant human life to a vampire? Humans are basically his food. You don't feel bad for the chicken that died so that you can eat nuggets. What's worse is that he saw his vampire wife die because of humans. He doesn't feel wrong for what he did, nor would he feel any different if he did it now except that he probably won't do it cause Gunchan would threaten to leave him. I like his character exactly because he's not your typical villain who tries to justify their wrongs, he's just chill fr.

bro idk why y'all love the side couple tbh the main couple is wayyy better imo like i can’t be the only one who is disturbed by the fact that ellian is dating his friend’s FATHER. ew. like not gunchan and minhoon going for the father and son pair HELPP. it’s even more crazy when u think abt how the author could have EASILY paired gunchan with hyungwoo’s BROTHER instead of his goddamn FATHER like pls. personally, i think the two of them don’t even have chemistry. what do they even like abt each other bc it felt like stockholm syndrome to me…
not to mention that ellian (the father) is such a fucking piece of shit and i personally don’t think he’s redeemable. still don’t forgive him for what he did to that lovely woman that hyungwoo liked. kinda crazy that he never even acknowledges all the horrible shit he did. he acts like he was always in the right.