either the kid died and time went backwards or IDK this is so confusing wth

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 ^_^