In a post at the exjw sub-reddit a user, UrsusAractus, posted a link to a site showing a secret ossuary/mausoleum built a few years after the Chiba Assembly Hall was constructed.
http://buta.exjw2.org/noukotudo/noukotudo.htm
As to why this is of note, he said in part:
In Japan, cremation is the norm for burials, and most either inter the ashes in a family plot (with many other deceased relatives) in a Buddhist ceremony, or bring them home to be placed on the family Buddhist altar. Witnesses, however, simply have the crematorium staff dispose of the ashes, as interring them requires a social obligation of visiting the grave, which is a disfellowshipping offense here (it's seen as ancestor worship).
Does anyone know about this? I've never heard of this.