It's pretty much obvious that Ji Wook hates Eun Hyuk so much, but why?


What is their relationship?


He even confessed his love for him. So cute! I'm looking forward for more of their bromance. (Or more like, one-sided bromance)


So far, I'm guessing it's because it was Eun Hyuk who slept with Ji Wook's ex? 


So far, that's what we only see whom she cheated with and we can't really make any assumptions...
But if he really did, it is indeed very hard to forgive him.


Nonetheless, I'm loving Choi Tae Joon's character so far, I love him! However, there can be a plot twist against him though....we might never know.


What do you guys think?
I'm thinking about this too, I'm assuming the same theory as you do, he cheats with Ji Wook's ex-gf, and maybe they break up after that (?), that's why he's trying his hardest to be close to his friend again :)
I love Eun Hyuk's character, so I really hope he's not the person Ji Wook's girlfriend slept with. If that's the case, It would be really hard to forgive him. Not just for Ji Wook, but as a viewer, for me too.
it would be too obvious if he's the one who slept with wook's gf. i'm assuming something else might've happened between them.
I also think that this ex gf thing would be too obvious...maybe he's some childhood friend he shares a special story with ????
on in the the description it said that they harbor some resentment towards each other due to family circumstances, or maybe I misunderstood something
If he slept with his wife/gf, why does he love him so much?  It doesn't fit.
This is my theory as well!
@Panda I just don't see the Eun Hyuk character *as we know him* doing something like that when he so openly adores Ji Wook.  The guys is saved in his phone as "My Ji Wookie" for heaven's sake.  :P

I'm not saying it's definitely not him (it probably is), but I don't think it's a believable plot point at this juncture.  Also, Ji Wook's hatred for him, while thorough, is not so dark as it would be for the person who slept with his wife/gf.  We'll see, I guess.
I think it's totally believable. My theory is that the older guy is his father and after JCW's father died, he lived with them, adopted. Therefore, they would be brothers, in that sense. Eun Hyuk could have made the mistake of sleeping with JCW's gf in a moment of stupidity and regretted it, but JCW refuses to forgive him.