While this article makes it somewhat sensationalistic linking it to welfare fraud, perhaps, the majority of "unregistered deaths" are the ones dying alone. The

While this article makes it somewhat sensationalistic linking it to welfare fraud, perhaps, the majority of "unregistered deaths" are the ones dying alone. There are so many cases in Japan that people die alone, and people not noticing it until their neighbors reports unusual odors, which may or may not happen. (although census should supposed to be catching that...)