Though there's a saying that goes, "Good deeds bring good rewards," Mr. Su Bai still doesn't believe that everything happened because he avenged the prematurely deceased children here. On this level, ordinary wandering spirits really have a hard time playing any role, which Mr. Su Bai clearly sees.
If he were a scholar rushing to Beijing for the imperial examination, lost in the woods, and then a little ghost came out to show him the way and help him escape danger, that would be believable. But the people involved now, whether it's Mr. Su Bai, Lucky, or the one lying in the coffin at the Land of Enlightenment, are not entities that a little ghost could connect.
