Conversation so far:
What was the Cultural background for the Departures (2008) film?
Japanese funerals are highly ritualized affairs which are generally--though not always--conducted in accordance with Buddhist rites.
How do the Japanese funerals go against the grains of Buddhist rites?
CANNOTANSWER.
What else can you tell me about the cultural background for the film?
Despite the importance of death rituals, in traditional Japanese culture the subject is considered unclean as everything related to death is thought to be a source of kegare (defilement).

Question: What was the greatest cultural background factor affecting the film?
Self-contained rewrite: What was the greatest cultural background factor affecting the 2008 film Departures?