The series teased it already with them visiting the power spots and Yui accidentally making a recording of a ghost, but it seems the series actually chose to breach the supernatural threshold. I think I'm done at this point, there is nothing the manga can do to justify continuing reading it. It doesn't seem as if Janice is a con-artist like someone suggested either,
so I can only hope it can still be explained with hypnosis/ suggestion, but I doubt it.
since in the next chapter it seems as if the ghost is possessing Junichi,