Does anyone know why he doesnt remember what he did is hs?

I read the novel a long time ago, but if I am not wrong, it was because Jiwook sustained a severe injury during his youth, rendering him with amnesia or something. Even Juyeon wouldn’t have enacted his revenge on Jiwook had not the man himself says about it.

When Jiwook woke up from the injury, Juyeon was there and asked him something about what would he do to someone who did him wrong. Obviously, Jiwook as a violent little cunt he is, replied that he should take revenge. So, yeah, Juyeon enacted the revenge because of Jiwook ( at this point, Jiwook doesn’t remember Juyeon anymore because of the amnesia ).