Sorry for the delay, I'm glad the anon could hand you the interview link.

For what I could gather from nugatory42 (and I still have pending reading those novels) is that the hourglass does not exist, it is but a representation of Kanda's strongest wish/desire which is to find that person no matter how long it takes him.

And yup, it can be that Zhu Mei feels guilty and is pretending Kanda is dead in order to let him have a reasonable easy life from now onwards.