Time is 100% going backwards because they failed a "mission", I also believe that the friend died. Perhaps the curse that imprisoned them is the friend?
After all, the friend last words were : "its fine, i can live this over n over again if it means staying with them" so he is probably aware that this isn't reality. Anyways, these are just theories. ITS SM FUN ^_^
That's what I was thinking has well and in chapter 13, there was a boy that referred to michan using his name. He didn't have a face but I think it was the friend he had blood running from what it looked like his head either he was beaten to death by his parent or he died attempting to save Minchan when he fell from the building? So the dream is to 'save' the friend
either the kid died and time went backwards or IDK this is so confusing wth