Notes

the thing about yi hyun is, how ppl can misread his character/narrative is bogged down with where you put his type of character, villain or antagonist. if your pick is he's a villain / turned villainy then you're bound to miss the wonderful contextualization of his character.

(both can be interchangeable but not always. villain can be antagonist but antagonist is not necessarily a villain.)

he is against yi kang's and everyone's drive (or path) but he is not on a true evil axis, just happens to be postured as the villain as he deviated from the design of 'goodness' as exhibited in yi kang's. if you choose to see him as a villain it's oversimplifying the complex nature of the character and ysy's nuanced potrayal. in short, you've just missed a greatly written (and acted) character (a non protagonist at that!!) that's still quite rare in kdrama writing.

trying to box the characters with hero vs villain is completely reductive and downright missing the point of the story. yi kang is not a true hero, general nokdu isn't one either. no one. because it's simple, jhm writes them in clear distinction from the basic of a story telling, protagonist and antagonist. so moot point trying to dictate which character is a hero which isn't.

(same principle here, hero and protagonist is not always interchangeable with each other.)

in other words, imho, what jhm is trying to do with nokdu flower is how we oft get too comfortable in putting characters according to what we think is bad or good when realistically, no one behave in such constant arc and he really push the stereotypical out of the way by saying the hero of the story is hope and tenacity and the villain is circumstances and dare i say, time. not any one of the characters.

also i think in more simpler terms, did yi hyun ever regards himself as the hero or a good guy even, in his turn towards dark and doom. no. he is simply reacting based on his ideals and thwarted ambition. he never cop himself as the hero and that's usually the basis of a villain, to think themselves as a hero with their own twisted reasonings. and that's also why the vacillating of the character is well realized and true, and he never cross the line of true villainy. what he is, he is well antagonized. the vacillating and reacting based on ideals etc are all committed by the other two leads, yi kang and ja in too so if you're saying yi hyun is a total inconstant wreck then what about the other two. no one remains stagnant in life.

as closing, i'm driving my point home with;
baek yi hyun is a well written character, one where it's clear jhm loves to write basing on his continuous interest on him also an antagonist at that, that it's been such a joy watching him being allowed by writing (and performance) to keep going on like this. i know he will end up dead if not physically but in some other way perhaps (big if if jhm wanted to break the expectation once again who knows) but you know.. when a character that's been doing the fucking most while he's alive, it's okay, it's the journey that matters, not the end, not really.