Conversation so far:
What is the cultural background in regards to the 2008 film, Departures?
Japanese funerals are highly ritualized affairs which are generally—though not always—conducted in accordance with Buddhist rites.
Are there any other interesting aspects about the cultural background of the 2008 film, Departures, besides how Japanese funerals are highly ritualized affairs?
Despite the importance of death rituals, in traditional Japanese culture the subject is considered unclean

Question: why is considered unclean?
Self-contained rewrite: Why is death considered unclean in traditional Japanese culture?