Responses
Now I feel like I should ve read till the latest chapter before commenting
He was real but he died when both he ang Myunghan were kids, probably because of a traumatic accident.
Myunghan saying that "everything fely like his fault" means he felt guilty for some reason and probably developped a psychologic disorder allowing him to keep seeing hallucinations of Yoon as a coping mechanism.
Is the red head guy actually dead/imaginary friend,like why dafuq everyone else behave like that, my intuitive powers say he is either imaginary or ghost!